Roost design/diameter/width

I use a 2x4 on the flat, so they can stand on the 4 side. This gives them plenty of room.

 

I use cut trees and branches that are about 2-4 inches in diameter.

 

You don't need to do anything to a tree branch. At four months, you shouldn't have to change roosts, they will not get that much bigger. Diameter would be big enough that they can't wrap their feet around it.

 

I have one big wide branch, 2x4s, and 2x3s....You might consider providing a variety of roosts for them...

 

I dont thing it matters if its round or flat. Here in the north east flat is probably a little better as far as sitting on their feet to keep warm but mine prefer to roost on top of a pallet wall, probably too thin, but its what they prefer. They still have the 2x4 on the wall but its only 2 feet off the floor when they were young, they use that one mostly during the day I find.

 

I have 3" diameter trees that I cut down in the run and I have 2x4's laid flat in the coop.

 

I use 2" x 2" (actually measure 1 3/4x 1 3/4). They seem to get use to whatever you have around. I've seen sticks, boards, etc and they all seem to adapt.