I use saplings or branches, 2" to 4" diameter. Some of my birds roost in the rafters, which are 4" diameter fence posts, eight feet up. Others prefer the roosts three to four feet up. I have plenty of roost space, so they decide.
Hello, I am on this topic right now too. I need to redo our roosts and am hesitating between a ladder like the one in the picture above, or a series of horizontal roosts at the same height (which I would place relatively high - 3-4 ft off the ground - to preserve floor space in the coop and make it easier to manage the deep litter) with a small chicken ladder to help the ladies get up there at night. My main concern is safety for the larger, heavier gals, so it seems like a ladder roost would protect their legs better as they go up, but would they all fight to be at the top and not use the bottom rungs?
I had heavy birds, why I put the ramps up to the poop boards under the roosts...
...also why I change out the nest perch from a 2x2 to a 2x4, as they were having trouble navigating the 2x2.
See the pic in post right above yours.
Poop boards are about 34" off floor and roosts are about 8" above the boards.