NEVER EVER mix bleach and OxyClean!Saturate the moss completely , you could also do a 50/50 with bleach and oxyclean but your foliage may die. Moss will be dead within week and roll right off the roof.
Mixing OxiClean and bleach is EXTREMELY DANGEROUS! OxiClean breaks down into hydrogen peroxide. The reaction of combining hydrogen peroxide and chlorine bleach makes a chemical reaction and poisonous gases.