The first time you try them, it's like learning to a ride a bike all over again. Once you get over the fear of falling (you WILL fall, you just need to get over it) you'll learn to ride them. You do have to concentrate more as the rollers are only maybe 18 inches wide so small steering adjustments can send you quickly towards the outer rails. Quick, precise corrections are necessary.

The good news is that when you do fall, it's pathetically uneventful. I've gone off the side twice now while riding hard and all that happens in your front wheel hits the ground, you stopping pedaling, then you frantically try to get your foot unclipped to avoid falling.