What's a good home remedy for moss / mold on a shingle roof

What type of shingle,
How old are the shingles, what type of condition are then in.

Why are you asking for a home remedy, there are many good products out there. Fill a hose end garden sprayer with bleach, set it for a 1:2 mix and spray the roof from the ground. Best to prevent moss by installing a zinc stripee at the very ridge of your roof line. The rain will wash very small amounts of zinc down the roof preventing future growth. ZincShield zinc strips & LiquidZinc chemical stop & prevent roof stains from algae, fungus, mildew, mold, moss