I struggle to see why Coman isn't getting the chance at AM when that is the position he fits best attribute wise. I think he displayed some of his qualities against Udinese, but we also saw some of his limits, which has a lot to do with him being young and it looked a lot like he was in doubt about what to do every time he were in the box. I think him getting space and having two striker in front of him would do him good. If he has to start, might as well play him where he is best.
About Dybala, i'm in the same boat as everyone in here, can't wait to see him start. But i can see the point in going with players accustomed to our tactics at first and introducing the new guys not all at once. He will get his chance. But i think he should start against Roma, also because i doubt Morata has that extra sharpness needed in those games, since he has been out. Assuming Cuadrado won't have the chance to start since he just arrived, i would go with this:
Buffon
Licht - Bonucci - Chiellini - Evra
Pereyra - Sturaro - Pogba
Coman
Dybala - Mandzukic
We could start with Sandro, but he hasn't been with the team long, and we can only guess how far he's come in terms of gelling with the rest of the team etc. Allegri will know, but i can't wait to see him in action, maybe as a sub.