I use rollers with a fluid resistance unit. A VO2max interval on this set for me, seated, is about 25 mph. Other units may be different. A set of Sportcrafters magnetic rollers hits 350 watts at 25 mph and 800 watts at 40 mph. Anyway, I wouldn't buy rollers without resistance. Use is too limited. So for really cheap, I'd go for the insanely boring trainer. At least you can do some efforts on it. But for real, I can only recommend rollers with resistance. I have about 15,000 miles on my set, so I've been well compensated for whatever I paid for them.

https://www.sportcrafters.com/blog/t...ve-pro-rollers