I can't quite see where it ripped, but it looks like he used the correct fasteners. Wind is a destructive force and must be planned for. Odd that it tore right there, because it looks like it could have been easily anchored at the top of that wall. I am sometimes guilty of using less fasteners to aid water-tightness. The front/wind side does need substantial fastening though.
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our home ,workshop, and 3 coops all have metal roofs with a 4-6 inch overhang and it does not need to be bent down and really should not be bent down if it is properly installed.
We always put the tin roofs on with lead headed nails through the rib and not the field. I have been told that lead headed nails are politically incorrect now days, and that we should be using screws with neoprene washers. Well, in the Arizona heat, those washers die and rot out in a couple of years.
When we sided a barn with tin, we would use a pan headed sheet metal screw through a bottle cap applied in the field. They never pulled through the tin. Bottle caps are not easy to come by now days. Find a friend with a bar, they will gladly give you all you need.
it looks like the fundamental problem was that this genius just did not frame the roof out with an overhang. You simply can't have more than an inch or inch-and-a-half of totally unsupported roof tin without having it catch the wind and try to pull off, as yours did.
I do believe you will have to replace that piece; but it is not at all difficult, just remove those screws, slip the new piece in, and reinstall the screws (preferably longer screws, or if you do not have longer screws it might be worth squirting a little 'gorilla glue' into the hole just before you reinstall the screw. This will make it real hard to replace the tin in the future but I don't think the rest of the coop is going to outlast the roof tin, you know?
) You COULD cut a patch and apply it over the damaged area, but IME patches always remain more easily blown off and leak-prone, and I would not do it myself.
Before you replace the roof tin, tho, you need to get supports built for it. If you are not inclined towards carpentry I think I am still going to go with my previous recommendation that you get some very strong, galvanized or otherwise outdoor-type angle brackets of some sort, at least 6" long on each leg and VERY THICK AND STRONG (ideally with a third piece across the hypotenuse, making them triangular rather than L-shaped), and use those to support add-on pieces of 2x4 that run essentially all the way out to the very edge of the roof tin. Screw all that on first, then screw your roof tin edge to that, and you should be back in business.
You don't get real high snow loads where you are, do you? That looks like it may be rather thin gauge metal, to rip that badly and to have been bought as siding rather than roofing.