You have to keep up with it.
But for most houses, it’s not an issue doing so.
Your landlord’s barn is a different issue. Flat roofs are in more danger of collapsing, but are also easier and safer to clear.
Insulation goes a long way to preventing ice build up thus allowing for easier shoveling.
That barn had no insulation. Farmers don’t insulate their barns around here. And the angle of that roof combined with 2 ice storms was a disaster waiting to happen.
That’s not a flat roof. It’s known as a mansard roof. It has 2 different angles.