From what I understand, roosts should be 2x4's with the 4" side being the one they stand on. Or at least something that is wide enough for them to stand flat footed on. Both because they aren't meant to grip rounds like your average bird and because they can get their feet completely covered up with their bodies when it's cold. I have 1x4's in one coop and 2x4's in the other, with the 2" side up, but that is getting changed this spring. I know everyone is different and prefers different things, but that is what I'm choosing to do and the reason why!
Yeah I use 2x4's (not pressure treated). 4" side up otherwise their toes will get frost bite. Don't use 2x2, not wide enough. You could use really thick tree branches as well, just make sure that when they sit on it, their toes are covered.