I happen to like rollers with a resistance unit on them. You can do a lot on rollers with a resistance unit - steady state Z2, one legged pedaling, tempo intervals, FastPedal, TT tests, and all sorts of aerobic and anaerobic intervals. I've hit on a workout schema where I ride rollers for 1 hour to 1:45 (my personal boredom limit) using different workouts on different days of the week, and then twice a week I go to the gym after my roller workout and do a circuit workout, like Friel suggests, with one set of 30, working almost to failure. Takes 20 minutes. I've tried a lot of different weight workouts over the years and this is what works for me. Every one's different. I never get injured doing this, and that's critical. Plus, a hard weight lifting regimen is a big training hit. I find it cuts down on my ability to put in hard cycling time and that's not so good. Another thing I like at the gym is the StepMill - one of those endless stairs machines that looks like an escalator. Ride that thing for over an hour in Z3 and your legs will know you've done something. It's something different to do in the winter and helps my out of the saddle power.