Dybala is a free agent meaning he's currently out of contract with Juventus and has no club. He will be open to opportunities at the time and whether he chooses to join Roma will depend on his priorities, if he wants Champions league football then Roma would be out of consideration because they won't be playing in the champions league next season but he might be assured of more playing time at Roma if he prioritize getting playing time so as i said it all goes down to his priorities in making a move.