Massage balls — from lacrosse-ball firmness to softer spiked versions — apply the same rolling pressure as a foam roller but concentrated on small areas: feet, calves, glutes, the muscles around the shoulder blade.
The peer-reviewed literature groups ball work with foam rolling under self-massage or self-myofascial release, and the 2019 Frontiers in Physiology meta-analysis of that literature reported small pre-exercise gains in flexibility and small post-exercise reductions in soreness and performance decline. Individual studies using balls on the foot and calf report short-term increases in range of motion consistent with the rolling literature. As with rolling, the reported mechanism is largely a change in the nervous system's tolerance of pressure and stretch rather than physical remodelling of tissue.