The issue is him showing no promise, potential, spark or special qualities.
Even in his Brazilian league videos, I thought he looked bad.
Roque was never a physical specimen, Barca knew that when they bought him.
Think of David Villa, he wasn't tall, he wasn't strong, he wasn't quick, he wasn't good dribbler or that superb technically.
But Villa was an assassin, he knew when and where to be, he knew how to finish.
In comparison, Roque is actually more athletic and stronger than Villa ever be, only an inch shorter and his touch will always be heavy. But his biggest assets is that he relentless and smart and good finisher. Those are the traits need to translate in Europe to be be a starting 9 in the top teams.
Currently it is a new set up, he isn't in a defensive oriented team as he was in Brazil, he isn't getting minutes as he was, he is coming back from injury while in Brazil, settling at higher level etc etc.
That isn't to say he will surely turn good, players fail all the time. But for me I think the most determining factor will be his finishing, a bit like Ferran it isn't great to get chances if you waste them.
Roque, even during his early struggles, showed he can still get chances, and as he settle more and get more in rotation he will get more. If he score them fans will forget about his struggles.