I will say that there are some roofs that are impossible to clear. My barn was one. In that case prayer might be the answer.
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.