Look, just because Roko isn't starting, doesn't mean he won't be good in the NBA.
Look at Macijauskas and Jasikevicius. They dominated in Europe but not so much in the NBA. Why? Because their game isn't suited for the NBA style.
Roko's game will fit perfectly with the NBA style.
He's very athletic, flashy, great 1 on 1, can score on many ways, defend, shoot etc.
The reason he isn't starting over Prigioni is because Prigioni is far more experienced than Roko.
BUT, whenever Roko gets the chance, he performs on a high level.
For example, last week he got to start and he scored 21 pts on 8-10 shooting vs Barcelona.
Roko still isn't a perfect player and his PG skills could improve but will average at least 6 ppg in the NBA if he gets the chance to play consistantly.
In Tau, he's not exactly getting much chance but when he gets the chance, he's great.
What he has proved to me is that no one in Europe can guard him one on one. That skill will translate to the NBA.