"Prickly roller – unsolved. Reposting after 8 years!"
A: "It pretty much is a tool similar to microneedling used in modern cosmetics, but it’s purpose is more that of pain relief (hence the thicker pricks compared to the needles in cosmetic devices), especially for sore or hardened muscles; works supposedly through enhanced blood perfusion, like a massage or capsaicin-ointment."