How much moss is on the roof. I would first suggest leaving it alone. Anything you do will dislodge granules and the granules are the protector of the asphalt of the shingle.
Now if you must try some kind of cleaner, go to your local ABC Roofing supply store and ask for Shingle Shield. Best thing I've found to clean a roof. Apply with a garden sprayer and rinse with a garden hose. DO NOT, I repeat DO NOT use any form of pressure washer.
I have used a product called Moss & Algae control by Worry Free Brand distributed by Lilly Miller Brands with not much luck. I used it with a hose applicator bottle and left it on for an hour before rinsing it off.
I Thank you for your for your suggestion and will look for that product Shingle Shield.