The cleaning of the north and east will remove the stains and bring back roof color to the same as the rest of the house. You would not see any difference unless the other areas are dirty. The SH and TSP will clean any asphalt shingleno matter what color. Your mixture will need to be adjusted to how dirty the roof is 50/50 SH and water with only 1 cup of TSP may be to weak especially if x-jetted. If you are going to do roofs invest in a delavan 5800 pump from Pressure-Tek, 200 ft of 5/8 chem hose, and a hose reel with a good ppoly sprayer to start. To do the best job for roofs from cleaning and protecting you need more TSP and add Borax and polmolive liquid soap to your mix. Look at the threads for "Applesauce" to get the right proportions for the mix and learn more about Borax and TSP.