How devastating. I'm so sorry.
I always hang heat lamps by a metal chain, to something like a rafter or beam. Other people have recommended having more than one attachment point on the fixture, as well. Even a clip on lamp can have a safety chain on it, to keep it from hitting the floor. These ideas are good for brooding, too.
If you need particular roosters for breeding, it's tough. If you don't, then I would try to pick a breed with a smaller or different style of comb. Some of the winter hardy breeds still have some pretty big single combs on the roosters. Maybe look at some of the roosters with pea or walnut combs.
You've already gotten some good building ideas. You could also think about making a more sheltered roosting area, that would keep a little more of their body heat in. They can be made out of different materials and be permanent or seasonal. Basically, it's a three sided box with a roof, positioned over the roost.
Good luck with your planning. I think you'll continue to get a lot of great ideas and support.