Use what you want but IMO if you were taking the industry and your business seriously you wouldn't have even asked that question, it's common sense. Time is money and margins are everything.
Hope I don't come off too harsh, it's just an opinion.
As harsh as roof-cleaning chemicals, you basteej! lol
Barry has the right of it, if you want to be serious, learn the business and do it right. Otherwise it is just a hobby.
Customers deserve to have services provided by professionals, with professional equipment, and professional insurance coverage, etc.
If you only clean roofs part-time, you still need to know the business, as your customers own that roof fulltime.
You may go to a restaurant and eat food prepared by a part-time cook, but he or she had better really know how to cook, or you will want your money back.
If you do few roof jobs, you can mix a smaller batch of whatever chemical you wish to use, but you should still use something that works instantly, like sodium hypochlirite solutions, or other recipes that contain it.
Do customers pay you the day you do the work, or when the roof is clean? Most of the experienced cleaners will anser, "Both."