I have two roost in my coop. One is about four feet off the ground, the other about three feet. Both are 2X4s wide end lying flat. I have poop boards under each roost. the height I have it at makes it easy to clean the poop off the boards. They are both high enough to clean without bending over.
I went with the flat 2X4 as I live in a cold climate and I believe this allows them to tuck their feet under them when they sleep to keep them warm. This is my first winter with chickens and so far have not heated my coop. We have had a unseasonably warm winter so far with the coldest only getting down in the single digits less than a hand full on nights.
Little off topic, out of the seven girls I am still getting six to seven eggs a day. I do provide additional light to extend their day. (about 14 hours as recommended here on BYC.)
A co-worker who also got chickens this year said his egg production is way down. He is heating his coop and has light on 24/7. I advised him in the fall not to heat his coop and provide 14 hours of light on a timer. He did not listen and now egg production is way down. At this stage of the game I would not recommend to him to turn off the heat as I am sure they now would have problems adjusting to the cooler temps.
I may turn on the heat lamps when it get down to a minus 10 for an extended period of time. I will have to monitor the girls to see how they are doing. My main problem is getting the eggs before they freeze. We loose a few but still have more than enough for the wife and I.