Teaching Rollfalls

One way our sensei teaches rolls is to have someone get on their hands and knees. Say you want them to roll over their right shoulder: Have them stick out their right arm straight ahead and at the same time, have them left up their left leg straight behind them. Then have them tuck their right arm (curved of course) behind their left arm. Tell them to keep raising their left leg up towards the ceiling and have them try to look in the direction where they placed their right arm. This should have them tilt into their roll and gravity takes over. This way he isn't really forcing the roll. The further he pushes his arm through, the lower he has to go to the mat.... so that might help too. Good luck!