Originally Posted by rubiksoval

Right.

That's the old school lore.

Now it's been shown that that's not the most effective way to pedal.

And leg speed really has nothing to do with any type of foundation. Cycling is an aerobic sport. Getting oxygen to your muscles so they can continue to work effectively is the foundation of it and any other endurance sport.

Rollers simply make you good at riding rollers, but I'd argue even that's a bit of a waste if you're trying to improve fitness indoors. If that's the case, a trainer will allow you to do proper workouts a bit more easily (though with resistance, I've done up to threshold workouts on rollers).