Are you working on your core as well?
Currently working on core with leg risers and weighted sit ups, will use the ab roller probably next week.
I'm also working on lower back with back extensions and with leg risers as this also works the lower back.
Core work, not directly. Squats done strictly work the abs as well. I get most of my middle and back strength from squats. I've used an ab roller and done correctly are brutal. My daughter was laughing her head off at me groaning whilst trying to roll back from extended position. My abs ached for days. I would recommend you do the exercise facing the wall, so the roller stops at a point which doesn't cause over extended injury. Pads or cushions for the knees.