Foam Rolling is a great rehab tool for all parts of the body. It can soften muscle adhesions leading to a faster recovery.
To foam roll the quads and hip flexors, lie on your stomach, supporting yourself with your elbows. Place the foam roller directly on your quad. Roll back and forth 10-20 times. Be sure to concentrate on any "sticky" points. Turning your foot in and out will help to get all the areas of the quad. To get more of the hip flexors, place the foam roller directly on the hip flexor muscles. Again, concentrate on any sore or tight spots.