Any group rides in the area? If so find the fastest group and tell them you don't mind if they drop you and then work on not getting dropped.
Solo, you can use your HRM and then do interval training. Warm up, hammer, rest, hammer, rest, repeat until you almost bonk.
Rollers will help your form - you'll ride a straighter line or hurt yourself, but it is hard to get enough load to help build strength.
Group rides and interval training would be about best... I do like the Nintendo factor of Compu-trainers and their ilk but the idea of riding inside just seems so retarded. Big fans and open windows during the winter???
I have rollers and prefer the idea of just bringing them out for drunk guests to try... j/k
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