Just relized. This is vitally important for realism.
In areas that get heavy snow, you will never ever see a flat roof. This is because snow will build up and it can cause your roof to become unstable and over a few years, can make an entire house unsafe and collapse the roof. Usually roofs would be made out of angled metal or shingles.
tl:dr no flat roofs, ok that mouse is a pair of slippers.