I went to the Hardware store this afternoon and bought a Simoniz soft wash brush with a 5ft handle, and some Full Timers wash and conditioner. I sprayed the roof first with a little water, then sprayed the cleaner on in 3ft squares. Went to town softly, then hosed off the foam. Did the whole roof then went back with a towel and dried the roof to wipe off the excess water and soapy solution.
I've posted the before and after. The after picture is not the greatest as there was a lot of shade when I was finished. When you are on the roof there are still some black spots but I get the feeling I could spend an entire day up there and they would still be there. From the house it looks like a new roof.
Not in the least bit intimidating, and as usual lots of useful info on Jayco Forums!