Recommendations

• Research the roof cleaning chemicals before choosing which ones to use.  for example, powdered or granular chlorine sold now for around $150 plus shipping by a competitor, will cause a VIOLENT EXPLOSION if mixed improperly with water. 
• Be aware of the chemcial compatiblity of your chemicals with your equipment and other chemicals.
• Understand how to respond to a hazardous chemical exposure, accidental release, storage procedures and shelf life.
• Strongly consider insuring your company against pollution release.  Most insurance policies do not automatically cover pollution caused by the chemicals used in roof cleaning.  For example, TSP or trisodium phosphate, is a pollutant under the Clean Water Act. 
• Always carry copies of all MSDS sheets for chemicals used in your roof cleaning and pressure washing mix.  Ask your chemical supplier for digital copies so that you may make more than one copy easily.  Use a three ring binder and sheet protectors for an easy to access reference guide.  It is against federal regulations for a supplier to refuse to supply a MSDS sheet.
• Always properly label your chemicals.
• Keep your chemicals organized and maintain a clean and well kept trailer or truck to detract the wrong kind of attention.  Throw out or remove empty chemical containers, used water bottles, food wrappers, cans, plastic bags and other unsightly items. 

(Please understand that these are only suggestions for you to think about.  Roof cleaning chemicals are inherently dangerous.  Arm yourself and your company with knowledge.)