Originally Posted by rubiksoval

How does it improve cadence? Anything you do with cadence you can do on the road.

How does it improve endurance? Probably erodes endurance because people generally train less indoors than they do out.

Balance? Any 5 year old that just learned how to ride a bike can balance. Rollers involve balancing in a particular spot in which you don't ever move from. Completely opposite of the road, in which you must negotiate turns, significant changes in speed, debris, obstacles, other riders, cars, etc. Totally different "balancing" needs.

Pedal smoothness? That's a nonsequitor as putting power to the pedals is not a smooth motion and in fact is more effectively done through a stomping motion, at least for higher power outputs, which is something you don't do on rollers.

Riding rollers makes you good at riding rollers. They have nothing to do with riding in a group or in a race. You get good at those things by doing those things.