I was watching DIY network this a.m. A commerical came on showing a man standing on the ground with a hose pipe connected to a container spraying his roof. Removing those ugly roof stains. Available at ace hardware. I have no idea of the cost. But I'm sure there will be some takers. We will have to be prepared to explain the negatives to.
It's more like "Spray and Regret" and it doesn't work. It takes multiple applications and sometimes up to 3 months to remove the stains, if it does at all. They normally recommend that you re-spray your roof frequently with their product to keep the stains from reappearing on your Roof. The stuff is garbage!