Remove moss from the roof with a long-handled scrub brush, a mixture of bleach and water, or a commercial roof cleaner. Another common method is to use a power washer, but this is not recommended, as it can damage the shingles.
Oxygen bleach is recommended for the bleach-and-water method because it is non-toxic and doesn't discolor the shingles. Once the shingles are cleaned, line the top of the roof with copper strips. Copper molecules that wash down the roof when it rains prevent future growth of moss and algae. Copper-embedded shingles are also available that work in the same manner to prevent future moss growth.