Rosen is a Pro Style or Pocket Passer style QB. It takes time for such a QB to see the game and process what they’re seeing. He needs to learn that he has a lot of playmakers around him and thus does not need to make THE play with his arm when it’s not there. Sometimes it’s just better to suck the ball down, run out of bounds, slide, or throw it out of bounds and go to the next play. He will learn that.
Dual threat QBs can have more immediate impact because they can safely bail a play out with their legs.