I believe a solution of clorox will kill the moss....but may bleach the roof and siding.
Why worry? Will it harm the roof?
Linda C

Sprinkle the moss powder on it...profusely. Give it a few days to kill the moss, then you should be able to get it off easily. Sprinkle it again with moss powder.

My dad used Spic-n-Span years ago. Just sprinkled it on. Of course by now the EPA has probably changed the formula.

You may want to do some tree trimming to get some light in that area & prevent regrowth too.

I remember a suggestion of weed killer from a gardening show.

I agree with jejvtr. Light will kill moss. If you have moss I have to assume that you have too many trees overhanging the house directly.

Roofing supply will have granules that you sprinkle on roof to kill algae. Lasts for about a year or so unless you live in a monsoon season area. Think its copper and/or zinc, sand like textured stuff. Hurts your hands, gritty stuff, wear gloves, toss it around.
Oxidation from the metals and those molecules running down the roof when it rains kills it and keeps on preventing it until it finally gets all rinsed off, or totally oxidizes over time. Little bit goes a long way.

But will it kill your plants when it runs into the yard? After all, algae is a plant.

Zinc & Copper are used in horticulture as trace minerals and here we spray it on citrus trees to eliminate and prevent the black sooty mold.

A copper wire stretched every foot across the roof will keep moss from growing. If you already have moss growing put powdered laundry detergent on it and water it down. It will kill the moss.

Use Cheap powdered Laundry Detergent. It is best to spread the detergent before a rain and let nature water it down. Also, powdered soap on a roof will make it slick even when dry. Is best if the work can be done with safety straps. Do not on any circumstance step in the soap in a larger patch. Ever hear of Humpty Dumpty?
His fall was from a wall. Yours will be from that roof.
I suggest safety straps.

There are companies out there that specialize in cleaning the moss off roofs. Moss and algae is a big problem in our area. Bleach will remove it but it will come back quickly using bleach and the bleach is not good for you or your plants. Composite shingles should not be pressure washed as this will damage you shingles. Roof cleaning companies do use a pressure washer but by the use of special tips, they reduce the amount of pressure which will not damage the roof. Cleaning the moss and algae from your roof is good for your shingles. The moss and algae acts like a sealer on your shingles which does not allow your shingles to breath. Do not go to a roofing company for advise, they will want to sell you a new roof and chances are, you just need your roof cleaned and not a new roof. Roof cleaning companies will guarantee that the chemicals will keep the moss off your roof for up to 10 years if you get a good company. The cost is minimal in comparison to getting a new roof.

I wouldn't apply bleach. We just had a new 40-year guarantee replacement roof put on. he roofers installed a strip of copper, which according to them "supposedly" creates a chemical reaction that inhibits algae. Also keep trees from overhanging is good advice. Sunlight is a great killer of mold, mildew, etc. Of course algae is a plant. But I still wouldn't apply bleach. Just too corrosive and toxic.

I used Spic n Span. Been about two years, don't see any growing back yet.

I was going to install copper flashing near the peak (like the copper wire suggested above) when I re-roofed, but I read that it can cause corrosion to my aluminum gutters, so I didn't.