Certified GKH Gardening Expert
You may want to try bleach. Bleach will kill the moss but breaks down into harmless elements in about 12-24 hours. Boiling water is another option. There are a couple of natural enzyme products on the market that work pretty well and are actually healthier than bleach. Ask your local hardware store about them. Also, shady roofs are magnets for moss, so if you have quite a bit of shade, you may want to consider having some limbs or trees removed to bring about more sunlight.