Roof Clean Chems
Raw chlorine, or sodium hypochlorite, will clean the roof, in a sense that it will kill mold spores and sanitize bacteria. Being as powerful as it is, it usually cleans stains pretty well, depending on the dilution. It should never be used @ more than 30%, and a complete rinse is needed. It should be "misted" onto shingle roofs, and saturated onto tile roofs (during your one hour set time you'll want to flush out the plants and shrubbery).
Sodium Hydroxide- Just like "sodium hypochlorite" is the polite name for chlorine, "sodium hydroxide" is the polite name for LYE. When roof cleaning was in it's early stages, LYE was used to clean shingle & tile roofs. Lye is Caustic soda, very dangerous stuff. So chlorine became the alternative. It was safer (not much, but indeed safer) and worked better. Now, as time has evolved, sodium hydroxide is the way to "not use bleach". But it's only history repeating itself!
"What's the best roof cleaner?"
Well, it's NOT chlorine... it's NOT caustic soda... it's NOT hydrogen poroxide or Trisodium Phosphate. It's not the spray on and forget chems, either. Go to home depot & get their roof cleaner. You can dilute every 1 gal of roof cleaner with 3 gals of water, and pull with your 20% (5:1) downstream injector. OR...it will work mixed @ a ratio of 1 gal roof cleaner to 7 gals water when applied direct (shur-flo, gas powerd app, etc). The cleaner's active biocide will turn yellow as it cleans, and 1 hour later your residuals will rinse away @ low pressure (using your 80 tip). After you're done, you can dilute @ 1 gal roof cleaner to 16 gals water and do a final "over-tone" (just apply a final application product and allow to dry, with no rinse). You can do that every six months on maintenance programs and the roof will never get dirty again.
Being a newbie, it's hard to afford non-chlorine chems. But the roof cleaner @ home depot is 22 bucks a gal... it's appx 45 big onez to clean a roof. When cleaning tile, you'll be using a mixture ratio of 50% chlorine, 50% roof cleaner (w/5 cups TIDE, 1 cup DAWN, 2 cups CARNUBA CAR WASH & WAX). Again, an overtone should be done. If you MUST use sodium hypochlorite, just be very careful. Always flush plantlife, and always rinse. Don't get near vinyl, glass, or cars.