A lot of people I work with in a rehab setting think that their low back pain is due to their lower back being weak, tight or a variety of other reasons. Quite frequently, however, lower back pain originates in the glute medius muscle. People with glute medius adhesions or trigger points often state that they have low back pain at the top of their posterior ilium or hip bone. Good ART practitioners and massage therapists will often work this area over, but the foam roller is a great tool as well.
Lie on your side with the "meaty" part of your lateral glutes (just posterior to the head of the femur) resting on the roller. Balance on one elbow with the same side leg on the ground and roll that lateral aspect of your glutes from top to bottom. If you find a “hot spot” or trigger point, it helps if you hold on that position for a 15-20 seconds. The foam roller isn’t going to cure the underlying pathology in your back pain, but it can definitely help relieve some pain and get you moving again!
Check out my Feel Better for 10 Bucks article for more great foam roller exercises.