You need rollers with a resistance unit. Performance has some reasonably priced ones. Then you need some workouts to do one them. I like doing one-legged pedaling intervals, very fast pedaling intervals, and lactate threshold intervals. Also try riding steadily in zone 3 and 100 cadence for a couple of 20 minutes intervals, 5 minute rest between. And building up to riding at 70 cadence in zone 3 continuously for an hour. Start with 15 minute intervals. All those things will really help your climbing, should you ever encounter a hill again. They're also pretty good for TTing.

Most folks don't want to spend a whole lot of time on rollers or trainers, so the thing is to push the envelope on them, so it takes less time to get the training effect. Otherwise, you'd be outside.