I train on rollers for 2 1/2 hours a day - four days a week during the winter. I don't buy the theory that you can't train or develop on rollers. I have ZZZing rollers (
www.zzzing.com - great, great, rollers by the way) with small drums, and you have to work hard on those small drums. I train on a converted $150 yard sale racing bicycle, 5 speed, with a 53 chainring up front and a 11 - 21 rear cassette that I made up. I also use 700 x 28 tires @ 90psi instead of thin, high pressure racing tires. Between the gears, tire size, and roller diameter you work your butt off. I got rid of the small chainring up front. I also stand on the rollers and this develops wonderful climbing skills because it makes you put your head forward, focus, balance, and again, you get so damn efficent in your circular pedal roation that it becomes an art.