Excuse me for being a trainer snob, but the Elite Parabolic Roller defeats one major point of riding free-standing on open rollers rather than propped up on a trainer.
According to a product information blurb on Cycles BiKyle,"Riding on rollers has never been so easy! Rollers improve conditioning and riding technique because the bicycle moves freely under the rider. The unique shape of the Elite Parabolic rollers give you more control making it much easier to learn. For the more experienced roller-rider, the Parabolic rollers require less concentration so you can just relax and ride!"
The flared ends of the rollers will guide a straying wheel back toward the center. This makes smoothness optional instead of desperately necessary. True, one should learn to relax and ride. In fact, you will be supremely relaxed, once you have mastered the smooth, circular pedal stroke and wobble-free upper body you need to stay up on traditional rollers.
One of my favorite games on the old "rollers of death" is to ride near one end. Then slide across to the other end. Flared ends will reduce the playing field and change the possible hazard. With flat ends on the rollers, a straying tire will drop into the gap and stop. Then, to paraphrase Jimi Hendrix, "excuse me while I kiss the floor." With flared ends, a gentle swerve will probably be met with a gentle correction. Sounds like an ad for a mild laxative. A sharper swerve could well result in a harsher laxative effect, as the bike high-sides over that lip. I haven't ridden the Elites, so I don't know where these thresholds might actually occur. I can tell from the promotional copy and by looking that the safety flange will take the edge off a beginner's anxiety and permit a higher degree of sloth from someone experienced.
Roller riding is an art. How can you live on the edge if the edge is fenced off?