Both roosts and bedding have wide ranges of 'what works'.
Some is personal preference or what's available.
I would say that a 2" dia branch would be the minimum.
Bedding can depend on how you manage the manure,
but yes I've seen folks use pine pellets.
The search function here can be iffy...
Good ventilation makes insulation moot at your temps.
Don't bother with it.
http://www.backyardchickens.com/t/1048597/ventilated-but-free-of-drafts
Here's a good article by RR about Space:
http://www.backyardchickens.com/a/how-much-room-do-chickens-need
....and some tips of heights indie the...