Rollers will square-off your tires.
I generally inflate my tires to the max pressure to ride the rollers. 100 PSI is great for conforming to pavement incongruities, but rollers are perfectly smooth. It helps reduce tire wear, especially if you ride the same tires on the road.

I can ride my resistance rollers at around 30 mph. If yours are that hard to ride, make sure all the belts are in place. Occasionally mine will move off-center, and it's noticeably harder.