There are two very different types of rollers. There's the usual set with aluminum or plastic rollers, just plain rollers. And then there are resistance rollers, a whole different thing. Resistance rollers have some way of increasing the resistance in one of the rear wheel rollers. The faster that roller turns, the greater the resistance. Some also have a mechanism for increasing the resistance without changing roller RPMs. Resistance rollers change the whole game. One can do intervals, change the steady-state resistance, etc.

The roller set I've been using for the past 25 years has resistance. I don't think I would have used them much without that feature. Mine have a very simple resistance unit, a fluid unit attached to one of the rear rollers. The faster the roller turns, the higher the resistance. Thus I control the resistance by shifting gears, holding the cadence the same or not, depending on what I want to work on. I can do 55 cadence intervals if I want, one legged pedaling, any sort of workout. So if you're thinking of buying a set of rollers, totally buy a set with resistance!

I admit that fancy $2000 trainers with all the whistles and bells are fun. But a set of resistance rollers will keep you entertained for a long time, plus they fold up and go away when not in use. Just staying up pretty much holds one's attention. I hate to be bored. Be sure to start using them in a doorway.