Modern Vespa

nope

Flat spots on rollers are totally normal with mileage, even with Grandma riding the scooter. Rollers don't always roll, they also slip and slide and jiggle and jostle as they get flung out during acceleration. At some point, the flat spots hinder that motion and the transmission starts getting ornery. The point of "sliders" is to provide a somewhat more-complex shape that accommodates this chaotic action for longer without distorting from wear.

No reason not to put rollers in good shape right back in after cleaning out the CVT. There does seem to be some debate whether treating them with a dry lubricant like Teflon is helpful in delaying the flat spots. I'm in the "no" camp on that one, because what goes onto the rollers can find its way onto the belt, which is no good.

nope