Is There a Safe Way to Pressure Wash a Composition Roof?

I have heard the many arguments back and forth on this issue of whether not to ever use a pressure washer to clean off a composition or architectural roof.
But then again I hear that there is a soft rotating on the pressure washing tip that can be used that will not damage or pressure off the granules from shingles. I know that we have used one and it is very good but do any of you use the soft tip head for pressure washing?
What are your thoughts on this topic as I am getting ready to put my spring marketing effort together using ad flyers distributed direct door to door plus other advertising techniques.