Using the right foot is crucial to your end result, and the roller foot does exactly that - it "rolls" along your fabric. This keeps the top and bottom pieces from slipping and moving as you sew. A must for all those hard-to-sew fabrics, like my gorgeous silks.
With the roller foot, much like another foot called a 'velvet foot', your seams end up as even as they started. Whether you are sewing vinyl, fleece, velvets, any napped fabric, or silks, polyesters, knits - this foot is the one to use.
Tomorrow I will cut into the lovely sari silk for my summer skirt! Temps are getting warmer and time to think spring!