Sounds like your learning to manage speed a little better that's always a good sign of progress! Keep an eye out for the bumpos, dips, ruts, etc., and a similar principle applies: keep those knees loose to absorb the chatter and that will prevent you from getting sent airborne inadvertently in those cases, too!
If you are trying to work up the skil and get comfortable with the approach speed - if you can make it out sunday (or any day one of us is riding) I speak for myself (but probably everyone else, too) you're more than welcome to shadow me and that will really help you dial in the right speed for the rollers. Basically I would ride as a "pace car" and I'd take that run at the speed you *need* to roll over it but not so fast that you'd get airborne. You'd follow close (but not too close!) and gauge your speed that way.