The more people you talk to the more different ideas you will get about roosts. Some people can feel pretty passionate about their opinions. And everyone can come up with studies or reasons why their way is best, whatever way that is. It's just something I find that people care about much more than the chickens do.
I'll link to where someone tried different roosts to see what the chickens preferred. Some people might find it interesting reading. This is only on what the chickens preferred, not what is best as far as supporting the feet while roosting. There are different studies that come to different conclusions on that.
Perch Experiment
https://www.backyardchickens.com/articles/the-perch-experiment.74272/
Some people want a flat roost, on the theory that the chickens will squat on their feet in freezing weather and protect against frostbite. What I see is that when they squat on the thinner roosts in cold weather their feet disappear in their feathers anyway. In Southern Florida that is not a concern for you at all. In my opinion as long as you don't get below -20 F (-30 C) that's not a big deal anyway, but that's my opinion. That's worth no more and no less than anyone else's opinion.
In my opinion roosts should be wood because of the heat conductive properties. Wood does not conduct heat well. In South Florida you are not worried about cold but it's possible too much heat could be a problem.
Chickens will roost on totally flat surfaces, like a shelf over 12" wide. I've seen them try to roost on a 3/4" wide piece of plywood on end. That's too thin, it's hard for them to stay balanced but that hen did. I kind of use the width of a 2x4 on edge as a minimum though I've seen them roost on tree branches thinner than that. as far as I'm concerned 2x4's are great, whether on edge or flat. If you use lumber I suggest you sand off the sharp edges whether they are flat or on edge. That's not because it is more comfortable for them to grasp but to remove the danger of splinters.
1-1/2" diameter or larger round wooden bars would work well as long as they are strong enough to not sag under the weight of the chickens. That's going to depend on the span. Tree limbs can work great too. My main roosts are tree limbs because they were available after an ice storm. I have a secondary roost with a 2x4 on edge because I had that available when I needed it and the way it was framed in on edge was easier.
I'll link to where someone tried different roosts to see what the chickens preferred. Some people might find it interesting reading. This is only on what the chickens preferred, not what is best as far as supporting the feet while roosting. There are different studies that come to different conclusions on that.
Perch Experiment
https://www.backyardchickens.com/articles/the-perch-experiment.74272/
Some people want a flat roost, on the theory that the chickens will squat on their feet in freezing weather and protect against frostbite. What I see is that when they squat on the thinner roosts in cold weather their feet disappear in their feathers anyway. In Southern Florida that is not a concern for you at all. In my opinion as long as you don't get below -20 F (-30 C) that's not a big deal anyway, but that's my opinion. That's worth no more and no less than anyone else's opinion.
In my opinion roosts should be wood because of the heat conductive properties. Wood does not conduct heat well. In South Florida you are not worried about cold but it's possible too much heat could be a problem.
Chickens will roost on totally flat surfaces, like a shelf over 12" wide. I've seen them try to roost on a 3/4" wide piece of plywood on end. That's too thin, it's hard for them to stay balanced but that hen did. I kind of use the width of a 2x4 on edge as a minimum though I've seen them roost on tree branches thinner than that. as far as I'm concerned 2x4's are great, whether on edge or flat. If you use lumber I suggest you sand off the sharp edges whether they are flat or on edge. That's not because it is more comfortable for them to grasp but to remove the danger of splinters.
1-1/2" diameter or larger round wooden bars would work well as long as they are strong enough to not sag under the weight of the chickens. That's going to depend on the span. Tree limbs can work great too. My main roosts are tree limbs because they were available after an ice storm. I have a secondary roost with a 2x4 on edge because I had that available when I needed it and the way it was framed in on edge was easier.