Lower Back Stretch
Lie on the foam roller , placing it on your lower back , cross the arms with both feet planted on the floor and using the foam roller as a fulcrum. It will be quite painful or sore . It will be less painful on your lower back by shifting most of your weight on the upper back and adjust the weight applied on your lower back by using your feet and arms on the floor for lift and reposition of your lower back. The pressure is effective by applying the lower back on to tense or spamming areas of the lower back for about 20 seconds on each area. This will give a deeper type of massage and release the tension in your lower back. You can make the massage more effective by bending one leg and straightening the next and leaning one side.
Spine mobility on your lower back
Place the foam roller on the lower back with knees bent , walk the foam roller up and down it will massage your para spinal muscles a bit . Roll the foam roller up to mid back . This exercise will mobilise your spinal segments. The exercise will will give you some core stability as well. Try not to arch and extend you back.