I should mention another general fact about trainers and rollers. People say they are bored on the trainer. That's the sign of a weak mind. I'm never bored. Hurting yes, but never bored. You should be concentrating on your form, your objectives for that ride, your progress toward those objectives, the entire time. I'll usually listen to music or even better, a news station to get the anger up. Never TV. The trainer is your only chance to work on pure form. When you're outside there are the other matters of traffic, tactics for overcoming hills, watching the road for nasty stuff, views, weather, other riders, all those other stimuli. Then you want your form built in, something you don't have to think about. Think about it on the trainer. Heels down, pedal round. Pedal circles or perhaps more correctly, pedal so that your trainer or rollers makes a smooth even sound. Back straight. Arms bent. Sit bones on the saddle. Head up. Shoulders relaxed. Even relax your legs. I know that sounds silly, but you can relax your legs and still pedal quite hard. Pedal with just your quads. Pedal with just your hams. Ankle. Don't ankle. Use all your different hand positions. On long trainer rides, I change hand positions every 5 minutes by the clock. I drink every 15 minutes by the clock. I stand every 10 minutes by the clock. Build the routine you'll use on the road. There's a lot to work on, a lot to hold your attention.