so this is purely anecdotal, but it's my observation thus far. I think i'm having a much easier time handling bike after riding on the rollers, mainly in the form of no hands riding. My c-dale used to swerve like a car driven by a drunkard when i go no hands, but no more. personally, i feel more confident in my handling skills, and as i was told, if i can remain confident and not tense up while riding, then taking a high speed turn gets easier.

Also, not to be glib, there are resistance units for rollers, and even on low resistance, the workout can get difficult in a hurry. Looking at my minoura unit, if all the roller drums have a groove for pulleys, then it's not so hard to attach a resistance unit to your roller.