I have a set of 3" rollers I bought from Performance several years ago for ~$100 and they've been champs. With a compact crank (50/34) and an 11-26 cassette I can sustain well over 300W, but I do spin around 100 rpm naturally. Rollers really do help improve balance, handling and focus. I once spent a month in the winter riding nothing but rollers before we got a break and I could get outside with the team. It felt like nothing could take me off my bike and my pedaling, line-holding and power were just so buttery smooth.