I looked at doing the same thing. I wanted to do reading for college courses while training. I finally decided that nothing could fully simulate road riding without some level of danger and gave up on the floating mechanism. Also, I don't know of any floating rollers that can fold up.

That said, you would have to spend time building/maintaining the homemade ones. The Emotions also have restraints that help hold the bike on the rollers. I would think not having them could pose a problem if the roller assembly snapped back/forth fast enough for the wheels to roll off. That would be more likely if you stood up and start swaying...the real reason to have the floating system.

I have both rollers and a fluid trainer. I would go the fluid trainer route if I could pick only one. It would be way too dangerous to let yourself get engrossed watching TV if your balance is as bad as mine. As it is, I use the rollers after the trainer so that my muscles are tired and have to work harder to keep balance. Both trainers cost me $220 dollars from PerformanceBike. I'm glad I went with a fluid trainer and cheaper set of rollers. Having both lets specialize on building power or balance.

Sorry for the long post, but I hope it helped!