I was assuming Vitor Roque was going to join by next summer just as Endrick will at Real Madrid. Roque is only 18 years old now. But he seems like a talented centre-forward for now. The number of goals he has scored so far is really impressive considering his young age. Barcelona signed him for only 40 million euros which could be a very profitable deal.
It is all up to Roque's adaptation level. If he does well with European football then Barcelona can benefit from his finishing skills and help him improve himself much more in the meantime.
I think signing victor Roque is a very good and profitable deal for Barcelona this season as he's going to serve in a very sensitive position which was vital and very much needed for Barcelona so it was a good deal for Barcelona as they did had a fair deal considering their current financial state which has in a way limited some of the actions the te would want to take.
Lewandoski is no doubt becoming aged and not in the best form to future I'm Barcelona game sand deliver the desired results of him, because the factor of his constraints is such that he can really fight as it's from nature itself which makes it quiet peculiar in his case. So just like you rightly stated, in the mean time victor will not be playing but will be watching around well enough to observe and get used to Barcelona style and patterns of playing then as soon as he starts he would have already gotten used to his new team and would play well enough to fit in the team when he starts playing with them.
Lewandowski is a difficult topic for Barcelona right now as on the one hand I think they wish he could perform outstandingly for maybe one or two seasons more until they really have a world class striker to substitute him. On the other hand the ties are getting loser between the player and the club as there have also been first arguments between Xavi and him and I think if Lewandowski doesn't score a lot of goals in the next few weeks, these cracks in their relationship will only get deeper and everything will get worse. I don't think they have a bright future together.