Foam rolling (and lacrosse/therapy ball or other myofascial releases) work by hitting trigger points. I pretty much knew this, but what I didn't know was there was another way foam rolling works to aid recovery, namely...
Foam rolling lengthens the muscle beyond what you can accomplish by stretching. For each technique she showed us for a particular muscle, Caron first had us stretch it with a conventional stretch, that way we could feel the difference the foam roller made. Apparently this is the recommended method even when you’re doing it at home.
The glute muscle benefits more from side-to-side rolling. For most people the larger glute muscles are long enough, but the piriformis muscle, not so much. Addressing this muscle requires a side-to-side motion.
Hamstring tightness is better addressed by lacrosse/therapy ball than a foam roller. I found this one to feel really weird (I wanted to complain to a grown-up about a ‘bad touch’ but the only one to accuse was myself). The ball has to sit just under the crease of your buttock and the top of the hamstring should feel like a thick rope that you roll over.
While I always thought of the lacrosse/therapy ball as a way to treat tricky injury spots, it can also simply be rolled under the foot to prevent plantar fasciitis, one of the most common running injuries.