This is a demo I did on a cedar roof.  I got the lead from a roofing company.  The roofing company and myself told the building owner he needs a new roof.  He still wanted a price to clean, so I did a small demo with a pump sprayer.(too many contractors in and out of building)  You can tell the roof is in bad shape. I sprayed and let it dwell about 5 mins.  It was around 45- 48 degrees.  I do a lot of cedar and I would say this is better than the greenwash/terrawash mixture.  The schmutz and lichens seemed to rinse fairly easy.  The dark reddish color on the finished slide is what I would expect and as it dries it should go to a lighter cinnamon color.  The bad thing about doing cedar this time of the year is that it takes forever to dry and you can't see the final color.

Yikes that's one of the ugliest cedar shake roofs I've seen...

I picked it up when I was in Florida thru J. Racenstein.  I don't know if it is on website yet or not, just give them a call.

That roof needs to go! Tim, your roofer handled that situation pretty well; told the owner it needs replacing but brought you in just the same. Very professional in my opinion.