So I'm in the market for a trainer. I figure this way I can ride everyday, at least a little bit. 1. Do they help with speed? My ex-bf was a roadie, and I remember him having rollers. I think he built the contraption himself (seems like it would be good for balancing) ... but these days all I see are these small sort of contraptions. I have no idea what to get. 2. Which is better? 3. Can you pick one up at a sporting goods store? 4. how much do they cost? Thanks!