To remove moss from the roof, scrub the affected area with a utility brush, then wash the roof with a solution of oxygen bleach, dish detergent and water. The process of cleaning the roof can typically be completed in a single afternoon.
Brush the moss away using a bristled brush. Begin at the peak of the roof and use downward strokes, taking care to avoid brushing off the granules that coat the shingles.
Cover any plants under the roof with plastic sheeting before washing the roof with the bleach solution. If plastic sheeting isn't available, spray the plants with a garden hose before treating the roof with oxygen bleach.
Mix 2 cups of oxygen cleaner and 1/2 cup liquid dish detergent in a gallon of water. Stir vigorously to completely dissolve the oxygen bleach, and use a garden sprayer to apply the solution to the shingles. Allow the mixture to remain on the roof for 20 minutes.
Use a garden hose to rinse the oxygen bleach solution off the shingles and any nearby plants.