Shawn, for those kind of roofs you have to be an aerial superman and tie off with repeling gear. In my opinion, all roofs have to be "washed" with 100 psi or so after you get the chem up there. I think I am in the monority though.
As an alternative, you can apply a higher concentration of sodium hypochlorite (in the 6%+ range) mixed with some TSP via a high flow gas powered roller pump and rinse using your machine and a large orifice 0 degree tip.
We do what our customers want as far as rinsing or not.
We have found over 15 years doing just roof cleaning that UN Rinsed roof stay clean longer, and even look better in the long run.
We honestly lay out both options for our customers, and let them decide.
90 percent want the longest cleaning possible, and so wait on Mother Nature to rinse.
However, the roofs look great when we leave.
If there are spots, we touch em up with the chemical solution.