I got a 2 yr old rubber roof that I have had a tough time trying to keep clean. The mold spots have wanted to stay no matter what I do to it UNTIL........
I was talking to the people that installed the roof and asked then about using 30 Second Cleaner. They said that it works and does it ever.
I put it straight strength in one quart garden sprayer and sprayed the roof and let set for about 5 min. Then used a wide angle pressure washer set a about 2000 lbs. I then washed the roof and WOW extreme clean without all the scrubbing and hard work.
It did not bother the finish on the side walls as I pressure wash the rest of the unit after the roof was finished.
Try it you'll like it. Worked for me. T he product is called 30 second cleaner and you an get it at Home Depot or Lowes.