You should be arching. You should be setting, and honestly, you shouldn't be learning it from a roundoff or learning it wrapped. If you have to wrap it to land it, you shouldn't be doing it on the floor, and doing it out of the roundoff forces the set, so it doesn't require you to learn a proper set. You should be learning it out of a BHS. You need to be blocking confidently out of your BHS, snapping a little shorter than you would for a BHS series, setting up for the tuck, and pulling your knees up. That should initiate the rotation and there should be no need to wrap. If you have to wrap to get over , the knee pull isn't strong enough and needs more conditioning.