If you are doing three spinning classes per week, I don't see why you would need rollers or a trainer. I got a trainer because I ended my membership at the gym (the spinning instructor that i really liked left and the others weren't worth the monthly fee).

Are you training for racing? When I did two spinning classes per week a few years ago, I was in great shape when the weather cleared up in the spring. It should be fun, and sometimes going overboard makes it not so much fun (called overtraining). You'll have to find where your limit is, though.