This association used to put out a paper newsletter and was very useful. The creator of the association has resurrected the website and updated some of her useful articles. I find much of it useful. https://www.fibromyalgiafund.org/lifestyle-changes/
I have fibro and much prefer softer surfaces, as the web site points out. My mattress is very supportive, but has a layer of gel on top, which feels soft, just heavenly. Physical therapists often have patients lie down on hard, high-density foam rollers to help relax the back muscles. I did this once at a PT clinic and ended up with a huge fibro flare. I was able to find a much softer one, but they aren't standard. In a novel I read recently, the main character's husband is a physical therapist. The late middle-aged protagonist doesn't have fibro, but does have arthritis and aches and pain, so her husband got her to lie on a hard roller. She said it must have been invented by someone who hates everybody. Some people use the hard ones comfortably, but they are awful for people with fibro and other pain conditions. Physical therapists undergo very rigorous training, but I've found they aren't familiar enough with the needs of fibro patients. If you push us too much, even though someone without fibro would be fine with that level of exertion, we will flare and could have pain for days.
Yeah, I've been rolling on a tennis ball to unknot the excruciating tender points upper mid and lower back and glutes. But I avoid it 'cause the tennis ball is not as tempting as the toddler's softer, air-filled plastic ball that I used to have, for years. Amazon searches are futile, so I need to have the energy-time to visit a store like Target kid's department. Been on my floating list for several years now. About 3-4 inch diameter, not foam, not hard.