[Aiwendil]

Looking at this issue now, I would rather use this part. Why, because as Aiwendil has posted, in the Quenta Noldorinwa, there is the mention of Rog and of his deeds in the battle. I would remove his slaying of the balrog because in the two instances where a single balrog was defeated in Gondolin, the battle was described as an elf vs balrog.

I am inclined toward this as well, but the difficulty is that this would require the fabrication of some text to describe the outcome of Rog's attack. I cannot see any other way of doing it at the moment.

we would either use a generic name like captain of the Hammer of Wrath or an enmended name such as Polwë, etc.
I would personally retain the name Rog or try to fit in later Sindarin or Quenya.

Of course we could try something like "Polwe", but any such solution would be quite arbitrary and not very good. It would be best, of course, if we could update Rog into later Sindarin. But we cannot. The element "Rog = strength" is not attested anywhere but in the Lost Tales, so we don't have some updated etymology to use. Nor is "Rog" unsuitable for any specific phonological reason that I can think of.