Roosting Poles?

It depends on where you live.

If your climate never gets really cold, it doesn't matter.

If it gets well below freezing, the widest roost you can provide will work well.

If you look at the birds when they're roosting and you can see their toes, the roost isn't wide enough.

We've had a mild winter so far but it can go below 0 here in the mtns., we put in 2 x 4's and our girls seem to love them, they are always on the roost at bed time. I think that a 2 x 4 laid flat gives them more stability, IMO. I hope this helps.

We are currently in the process of building our coop. I saved a big tree limb that fell during a storm a few weeks ago for a roost. I'm all about free. 

I found some bamboo that works well. Here's my quail roosting on it but I have it in my chicken houses as well.

Flatter, wider roosts are better for chickens' feet than perfectly round poles or dowels. You can use natural tree branches, but make sure there are no sharp spots that could injure feet, and pick branches that are a little wider than your chickens' foot. I sand down any rough spots on the branches I use, and also spray the branch thoroughly with Adams Flea and Tick spray, then leave it out in the sun to dry and air out. 

I also use pine or aspen boards, 2" wide for my tiny bantams, with the edges sanded down. 

We have a lot of bamboo growing on our property, but I've read that bamboo is too slippery for use as a perch even for perching birds (parrots, etc.), so I don't use it for that purpose.