We are in SC and my husband is using bamboo
He attached some 2x4's extended from the wall of the coop and then attached bamboo from the 2x4's.
Our ladies love it!
I went down to my local bargin/recycled building materials place and got 2" round closet poles. They are big enough around to fit my heavy hens' feet just right. Also, one side of the poles is flattened if you have hens with smaller feet. I can have an 8' long roost hanging up without needing any support in the middle. I have two of these crisscrossing my henhouse, holding up 13 heavy hens. Also, since they are only 2" around, no poop builds up that would need to be cleaned off like a flat 2x4 would. My hens do quite well at keeping their feet warm just by sitting on them with temps getting down into the high 20s and low 30s here.