I've had good luck with 2x4s wide side up. The girls stand on them rather than perch, but I've not had any problems with frostbite, not even when outside temps were -14 (that last coop never got colder than 14 degrees even under those conditions) and no bumblefoot either since the 2x4 edges are rounded a little. As for when they get dirty, I just scrape off what will and don't worry about the stains. Roosts are, to me at least and not knocking anybody else here that feels otherwise, a functional rather than fashionable item. A little dirt won't hurt.
And if you're worried about the roosts emitting ammonia, try putting on some gloves and a mask and rub a little neutralizer on there after scraping them clean. Only a little mind you, think in terms of a sprinkle, not trying to choke the chickens or the human.
I like the idea of using tree branches, but find the idea of installing them to be a little daunting. (Also don't have trees that big at the new place.)