As they say, "you can't ride on water unless you have POWER!"
It all depends on on how fast you pedal. At 5 mph you need about 50 Watts of power.
At 40 mph You need about 350 Watts. This of course depends on tire pressure, size, drivetrain efficiency etc. Also if you ride at the outside edge of the rollers it takes about 10 Watts more as the resistance is higher.