Jared Goff? he didn't play as much but 5 TD 7 picks 54.6% and a QBR of 18.9. Maybe he'd have gotten better if he'd played more but remember the reason he didn't play more is he was so clearly in over his head in preseason and camp that they didn't want to play him.
Now that doesn't mean Rosen is going to put up 28 TD to 7 INT in year 2 like Goff did but their rookie years were quite similar, Josh just played nearly twice as much.
My big concerns on Josh, all the late throws and backfoot stuff that's really bad habits he got into. the pick six stuff, way too many of those. The continuing to make the same mistake all year long.
The stuff you like, great arm, very bright kid, we don't know yet if it translates to football smart, again he threw lots of INT's in college too said that all along, but he's VERY smart. it's not a case of him not being able to understand, it's the game slowing down and in his case it had to REALLY slow down because he had such bad protection this year. Goff was arguably worse except I don't think he threw all the pick sixes. He was 0-7 in games he started.
I have no idea how Josh is going to turn out, I expected him to get better this year and he didn't.