I don't think it has anything to do with wins, as much as to show consistancy, and be able to move the offense. I guess it has to be at least 4 or 5 if you look at the schedule.
If he continually makes great throws, but receivers drop passes, that will not be on him, and hopefully the coaching staff will keep that in mind.
If he is able to move the offense consistently and actually start scoring, but the defense leaks points back to the opponent quicker then Rosen can keep up, that can't be blamed on him.
If he is making great throws, great decisions, showing great awareness of the pass-rush, but the inffective O-line is not giving him enough time to do his job, that is not on Rosen also.
Rosen needs to do his Job well, and prove he could be a franchise QB in the making, and he could win a chance to prove himself next year with far better talent.