I never had much luck with the copper REMOVING the moss once it was established, but after I cleaned the shingles manually (very carefully, it was an old roof), I put copper along each side of the peak for about three inches. The rain (this was in western Washington - Issaquah), washed enough miscellaneous copper salts from the metal to keep the moss from coming back. Worked great. Two cautions: ground the copper and put up a lightning rod, and don't count on anything growing where the runoff from the roof hits the ground - it won't.
Pat