I have always thought this way -
ALL those dealers in NW NY State where the lake effect snows get turned on, or anywhere with heavy snow fall for that matter.. NONE get on and clean the roof that I know of...
Since I am still somewhat young, I will use a rubber squeegee if the snow pack gets DEEP.... just to clean off the outter 2' or 3' to allow the water to escape
I always am more concerned with the re freeze and thawing causing water to run into places it usually wouldn't..
Done that once or twice over the years is all....