How firm should a foam roller be for back pain?
If you are new to foam rolling or have acute back pain, start with a soft or medium density roller. Firm and extra firm rollers deliver deeper pressure that can be counterproductive on already inflamed muscles. Once your pain improves and your muscles adapt, usually after two or three weeks of regular rolling, you can graduate to a firmer roller for deeper myofascial release.
Full guide: Best Foam Rollers for Back Pain: Tested for Relief and Recovery