First, parabolic rollers are for wussy.
Second, when you make the rollers, make certain you provide some way of balancing the cylinders. It will be essential the rollers be balanced; they are spinning quite fast when you have the bike up to speed.
Third, I have no idea why a flywheel will "ruin" one's spin. All you are doing is simulating the momentum you normally get by having the bike in motion on the road. Stationary bikes have only the momentum of the wheels and rollers keeping the wheels turning through the dead spots of the pedal stroke. Bikes in motion have the momentum of your body weight at speed to keep the wheels turning. Adding a flywheel to rollers simply mimics what is already present by a bike in motion.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter