Get a big dog crate. Use something to fix the door, so it stays propped open, just enough for them to get in, and out. Cover the dog crate, except the door opening. Take a piece of 2 x 4, and cut two blocks from it. Cut the rest of it slightly smaller than the width at the back of the crate. Screw the longer piece into the blocks, so it's slightly elevated. This will serve as a roost. Put it about 3/4 of the way back into the crate. Put hay in the bottom of the crate. It should keep them cozy, warm, and provide enough air circulation. Put a decent layer of Vaseline on their combs, and wattles.