DwayneNLiz has given you good info on roosts - all breeds benefit from having 2x4 roosts with the 4" side up. Chickens like to have their feet in front of them and lay their heads down upon them to keep warm. Some folks also tack towels to the roost bar.
If you have an enclosed run, a solid type roof will provide some protection from rain and snow, as well as keeping raptors and climbers OUT. Sometimes silkies just prefer to lay in a pile, in the corner of the run floor. Silkies can jump high, but generally do not do much flying. Their type of feathered wings don't lend themselves to true flying.