Each Istari had a different mission?

[Rhod the Red]

Each probably was. The Unfinished Tales chapter
on The Istari addresses these. Though it was
more, as far as I can see, the reaction or
treatment that defined the Istari.

Saruman may not have gone bad if he wasn't
grovelled so much by M-e leaders. If, for example,
(forget his name) the Steward that gave him the
key to Orthanc never did that or allowed him
access to the Minas Tirith archives, lack of access to
the Palantir & a fixed abode may have mitigated,
if not prevented, his evolution of thought.

Gandalf got fair treatment, but not 'special treatment',
as it were. So his ego wasn't tickled to inflate. Radagast
ensured he lived humbly and in 'Wild' lands on
the west side of Mirkwood. Nor did he zigzag and
seek grovelling. The Blue wizards? Who knows.

So in a way, when you think about it, the themes and
flow of the story tell us more about how they are treated
by other characters than their inherent skills. We get
hints of Saruman & Gandalf being lore-masters, but not
the full picture. And their decisions influenced by what they
saw/did in Middle-earth.

[Legate of Amon Lanc]

Originally Posted by Rhod the Red

Saruman may not have gone bad if he wasn't
grovelled so much by M-e leaders. If, for example,
(forget his name) the Steward that gave him the
key to Orthanc never did that or allowed him
access to the Minas Tirith archives, lack of access to
the Palantir & a fixed abode may have mitigated,
if not prevented, his evolution of thought.

I don't entirely agree. I agree that probably getting Orthanc further inflated his ego and gave him the excuse to lock himself up and start building his own little empire (not to mention the temptation of using the Palantír, eventually), but it certainly wasn't the only thing. Certainly you can't say Saruman did not have it "in him" to be the authoritative type. I am not sure if I recall correctly, but I think he asked for the keys of Orthanc in the first place. And in any case, you can see already in the Unfinished Tales, in the description of the Council, that he had this desire to be the "First" with everything that comes with it (he was jealous of Olórin already there, that much the text implies).

And lack of access to the archives - that is ridiculous. Saruman (or in fact, all the Istari) was supposed to help the folks of Middle-Earth, among other things, with their knowledge. A Steward should then come and say "hey, you have no permission to look into my archives"? That'd be pretty stupid, wouldn't it? Denying information to your allies sounds quite nonsensical to me. After all, it's only information - but what one decides to do with it, that is what counts. And as we know, Saruman eventually used e.g. some of the knowledge of Sauron's to (possibly) for example breed Uruk-hai... but that came from his own mind.

And as for Radagast, see above. Remember that he failed. Radagast was on the opposite end of the spectrum from Saruman, but they were both extreme. Radagast went so far in his, as you say, "humble life in the wild" that he got totally out of touch with the "real" world around him, out of touch with the Free Peoples and their problems. (Saruman had the opposite problem, he had forgotten that nature is something more than just tool for the humans. But they both made a critical mistake.)

[Boromir88]

Originally Posted by Legate

And lack of access to the archives - that is ridiculous. Saruman (or in fact, all the Istari) was supposed to help the folks of Middle-Earth, among other things, with their knowledge. A Steward should then come and say "hey, you have no permission to look into my archives"? That'd be pretty stupid, wouldn't it?

And according to Gandalf Denethor was more welcoming to Saruman perusing the Minas Tirith archives, than when Gandalf goes to Minas Tirith and reads Isildur's scroll:

'With that thought, I forsook the chase, and passed swifty to Gondor. In former days the members of my order had been well received there, and Saruman most of all. Often he had been for long the guest of the Lords of the City. Less welcome did the Lord Denethor show me then than of old, and grudgingly he permitted me to search among his hoarded scrolls and books.'~The Council of Elrond

If anything, Saruman was the Istari member who spent a lot of time in Minas Tirith's archives and as a welcomed guest of the Stewards.

The two Blue Wizards are perhaps the trickiest of the bunch to reach any conclusions as. As far as Radagast, I agree with Legate his apathy and laziness to completing his mission of rallying suppport to defeat Sauron meant he failed, however he had never "fallen" to evil. Just as there is evil that exists in Middle-earth, completely independent of Sauron, with a strong power of its own (think Old Man Willow), there are overall good forces yet rather apathetic towards the fight against Sauron.

The Blue Wizards are slightly different, because it seems as if their fate is unknown. They travel East, with Saruman (but do not return), and perhaps start cults of their own, or perhaps just die and have very little impact on the events of the Third Age, primarily dealing with Saruman. But in his late writings, Tolkien seems to revise and imply Alatar and Pallando have a huge effect on the Third Age, curtailing Sauron's influence in the East. That Alatar and Pallando were sent specifically to the East (lending credence to TheLostPilgrim's post of each Istari having separate missions) and their actions in the East swayed many away from Sauron who's forces would have simply overwhelmed the West, had they not been sent:

But the other two Istari were sent for a different purpose. Morinehtar and Romestamo. Darkness-slayer and East-helper. Their task was to circumvent Sauron: to bring help to the few tribes of Men that had rebelled from Melkor-worship, to stir -up rebellion...and after his first fall to search out his hiding (in which they failed) and to cause dissension and disarray among the dark East. They must have had very great influence on the history of the Second Age and Third Age in weakening and disarrayinbg the forces of the East...who would both in the Second and Third Age otherwise have outnumbered the West.~HOME 12: Last Writings

The issue with this is it directly contradicts the published Lord of The Rings which states that all the Istari arrived in Middle-earth at the same time, and here Tolkien is writing the Blue Wizards impacted both the 2nd and 3rd ages.

However, it should still illustrated the point that, I believed all the Istari were sent with sort of a specialized mission, meant to contribute to the overall purpose of defeating Sauron. They were not meant to directly use their power to fight Sauron's power, but instead to use the powers in the people and creatures of Middle-earth to defeat Sauron. Gandalf clearly succeeds in this, with his constant weary fight in aiding Elves, Men, Hobbits, and dwarves against Sauron. Saruman was meant to do much the same, and perhaps use his knowledge of craft and voice to help. Radagast seems most likely meant to get the animals, creatures, and nature united against Sauron. While Alatar and Pallando were specifically sent East to do what they can in halting Sauron's influence in places like Rhun, Harad, and Khand.

[Rhod the Red]

Saruman was head of the White Council at the time, but Beren had no way of knowing whom Saruman really represented (the Valar). Nor
do we know why he cleared him access. While there's
the voluntary possibility, it's also possible he used his 'voice' power
on Beren too.

[Legate of Amon Lanc]

Originally Posted by Rhod the Red

Saruman was head of the White Council at the time, but Beren had no way of knowing whom Saruman really represented (the Valar). Nor
do we know why he cleared him access. While there's
the voluntary possibility, it's also possible he used his 'voice' power
on Beren too.

Saruman certainly was a charismatic figure from the start, so that surely might have played its role, but let's bear in mind that Saruman, at that point, was still "good", I would say as much good as it goes still, so he would not use his voice intentionally to manipulate the people. Probably. I mean, I would believe he wasn't still in the stage to "misuse power", or not on any conscious scale. It depends how you define his "voice", if you mean by it simply his charisma and personal rhetorical skill which he uses unconsciously, naturally, then yes, but I would not imagine he would "use Jedi Mind Trick" or "cast a Charm Person spell" (to borrow illustrative examples) for the sake of getting Orthanc. Remember also the situation: Gondor had lost its garrison in Isengard, it didn't have manpower to spare, giving it to an ally with the reputation of Saruman was almost certainly one of the best things to do even from the Steward's point of view. So no need for coerce or mind tricks.

[Rhod the Red]

so he would not use his voice intentionally to manipulate the people

That's speculation.

If we judge by how it performed in the chapter of
'The Voice of Saruman' it would have ideally
been used after Beren tells his servants to leave
so that Saruman's alone with him.

He wasn't 'good' then, he'd already said no
to an assault on Dol Guldor and if you check
the timeline at the back of TLotR he had already
searched the Gladden Fields, etc. Probably
already obtained the Ellendil Star from Isildur's
body. As well as at least got to the point of spying
on the Shire.

We don't know whether Beren saw the White Council
as allies. Presumably Beren could speak Elvish, like
all from the Numenorian line on Middle-earth. So it's
logical either Beren voluntarily gave him the keys to
Orthanc & Minas Tirith archives or he coerced him
when the opportunity came.

[Legate of Amon Lanc]

Originally Posted by Rhod the Red

That's speculation.

Of course it is, I said it's my personal point of view. But it's based on what we know about Saruman. He was still not corrupted by the thought about the Ring at that time, and for instance we know he still, for some time, had been discussing with Treebeard rather politely (asking him permissions if he could visit Fangorn at all and so on). He certainly would have wanted to have a base (since it was "cool" and gave him some more authority), but I think he would still be reluctant to "perform mind tricks" (see above my explanation of what I do and what I don't mean by him using his Voice), and, most of all, he would not even need to perform them.

He wasn't 'good' then, he'd already said no
to an assault on Dol Guldor and if you check
the timeline at the back of TLotR he had already
searched the Gladden Fields, etc. Probably
already obtained the Ellendil Star from Isildur's
body. As well as at least got to the point of spying
on the Shire.

That's not correct. Check the timeline. Saruman settled in Isengard at 2759 TA, he said no to the assault on Dol Guldur by 2851, which is also the year he started searching around the Gladden Fields (with the footnote that this was probably the time he started lusting after the One Ring). And obviously, it isn't even logical: he could not have started searching the Gladden Fields before he had a permanent base nearby, or found the remains of Isildur for that matter, since we know he had kept it in his treasury in Orthanc - which he would have to have in the first place. In any case, the timeline says it plainly and clearly.

We don't know whether Beren saw the White Council
as allies. Presumably Beren could speak Elvish, like
all from the Numenorian line on Middle-earth. So it's
logical either Beren voluntarily gave him the keys to
Orthanc & Minas Tirith archives or he coerced him
when the opportunity came.

We know it very well. In the Appendices, in the story of the Southern Kingdom, we read that after the Long Winter

...Gondor began to recover its strength. But Rohan was slower to be healed of the hurts that it had received. It was for this reason that Beren welcomed Saruman, and gave to him the keys of Orthanc; and from that year on (2759) Saruman dwelt in Isengard.

(emphasis mine, of course)

Another account of this is also in the part about the kings of Rohan:

It was at the crowning of Fréaláf that Saruman appeared, bringing gifts, and speaking great praise of the valour of the Rohirrim. All thought him a welcome guest. Soon after he took up his abode in Isengard. For this, Beren, Steward of Gondor, gave him leave, for Gondor still claimed Isengard as a fortress of its realm, and not part of Rohan. Beren also gave into Saruman's keeping the keys of Orthanc. That tower no enemy had been able to harm or to enter.
In this way Saruman began to behave as a lord of Men; for at first he held Isengard as a lieutenant of the Steward and warden of the tower. But Fréaláf was as glad as Beren to have this so, and to know that Isengard was in the hands of a strong friend.

We can hear the tone of wariness from the narrator, but that is only the narrator who knows (and the reader knows as well) what Saruman was going to become: but it is clear from the text that the rulers of Gondor and Rohan at that point thought of Saruman as a friend. Obviously.

There is another sentence in the following text, saying that Saruman "seemed to be a friend for long, and in the beginning he maybe was one in truth". The "maybe", true, makes it sound a little doubtful, but I think there is no need to think that he wasn't. (I mean, there is no "maybe" in the objective way of thinking; the "maybe" is merely the chronicler's note: but in the end, either Saruman was a friend, or wasn't. And I daresay he was, but what is even clearer is that there had been no doubt about him being a friend in the eyes of the Free Peoples - whether he truly had been one or not. In any case, you would not call him "maybe a friend" if he had been walking around mind-controlling people into giving him a fortress.)