Most of the races are flat here, but I live in the area where I could do hilly rides with 1500-2000m of climbing. Is there much benefit with that if I am racing flat?
While training on a stationary bike could never fully substitute time on the road, there are many workouts you can perform to work on a piece of your cycling.
Questions and answers on HIM training with a sprained ankle, metric century plan basics, Olympic speedwork, Ironman commuter rides, bricks, HIM before IM recovery and post race nutrition.