There is a precedent on teams now moving on from a QB within 2 seasons at times. Cleveland did that. Hell they did it twice if we remember with Brandon Weeden and Johnny Manziel. The Bengals themselves once moved on from Akili Smith within 2 seasons as well.
The only way this works is if they get a decent trade for Rosen and get a 1st and 2nd possibly value wise. But its how much they get for Rosen that matters here. If its anything less than at least 1 , 1st round pick then its a wasted selection and they deserve people laughing at them.