I don't have any exact math on roosts, but I allow 1 foot of roost per bird. so six feet of roost. I would use at least 2x2 preferably a 2x4 on edge. keep in mind chickens can get heavy fast. 6 slightly overfed rhode island reds, especially if they are production rhode island reds can get to 60 or more lbs.
I would certainly wrap it in some sort of wire. use wire to match the conditions you are in and predators you will have. I realize a lot of us also have to balance it to our budgets too. my minimum recommendation would be to use 2x4 welded wire lined with chicken wire. this will not keep a lot of predators out, but will at least slow them down a little. I also do recommend covering your chickens with something. some predators come from above, some below some direct on from the side.
my regular recommendation on wire is use 1x1 16 gauge welded wire. this is rather expensive the best price I can find on a 3 foot wide roll locally is about $170.
my strongest common recommendation would be cattle panels and 1x1 wire, this will pretty much keep anything out. probably not a bear.
if your putting your coop in a permanent location, bury some wire to help prevent animals from digging. as your flock and coop grows you may find electric netting or fencing necessary.
Edited by loveourbirds - 5/11/13 at 3:25pm