I agree w/Boro - I havent found any evidence that Saruman's ring was used in breeding UrukHai or anything else.
On Sauron's influence on the 3 - well from a technical point of view - if you have a blueprint of something (a building - software - anything) you dont need to be the creator to have an influence or impact on it. Now, if you had any hand at all in writing the blueprint - you have all sorts of ways to control or destroy or influence the product at any time. Thats how i see it anyways.
