Roofs are elevated locations. Falls from said places generally result in injury. Although I sometimes partied on roofs as a teen, I am no longer indestructible. I saw a man working on a roof right after a rain recently. This is an obvious no-no unless one has a very large life insurance policy. One time I was wire-brushing bits of moss off my front porch roof. A new neighbor yelled "Don't fall!" at the top of his lungs. I steadied myself, got my bearings, took a deep breath and thanked him for looking out for me. I was rattled for approximately one hour and I'm considering performing this task at night in the future. I know several people who are very nonchalant about walking on roofs. Apparently there is some bravado involved and I stand mute when I observe it to avoid possible wraith. However, ask yourself: "Do I have a body like a squirrel?". Nature gave us bipedal motion, not hyper-tree jumper motion. Think about it- especially in wet or winter conditions. Apparently the man below did not.
