When you master no hands over the rollers you can consider yourself good over them.
As for sprint standing up?? 1st time i heard about that in regular rollers, in the ones that swings and stuff you can do it because the darn roller will follow you and move with the bike but in regular ones i really dont advice you to do it, you will bounce out of it as you did already
The reason for the rollers is for cadence, sprint seated (high cadence) and to improve pedaling technique because at least the regular rollers wont allow you to do crazy stuff like standing for example (you learn that one already), keep your line and just go straight accelerating and round pedaling.
Good luck man.. those things work if used the right way.