To achieve the rolling, let gravity help you. The key to this is to avoid intentional tightening of your back or ab muscles.
Sources:
Kisner, C., & Colby, L.A. (2002). Therapeutic Exercise: Foundations and Techniques.Philadelphia: F.A. Davis Company.
Hage, M. (2005). The Back Pain Book. Atlanta, Ga. Peachtree Publishers.


