Same as for the house, just stronger. House mixes are usually 1%, roof mixes are usually 3-5%.
Downstream typical mix in a 5 gallon bucket for 12.5% bleach is 2 gallons SH to 3 gallons water. Adjust up as needed. Some people dont even cut it, but most say not cutting it is unnecessary for typical house washing.
Roof typical mix using 12.5% bleach for 50 gallon mix is 12.5 gallons - 20 gallons SH. That's 3-5%, direct application. Some people go 50/50. The stronger you make it, the faster it works, and the faster it burns up vegetation if you arent careful.