Most times it does not get that cold here, but they say it is going to be the coldest winter in 10 years. Most of my birds are in covered pens, the bottom is open in the summer but during winter I wrap the bottom in tarp. This allows the ground heat to rise adding a couple degrees, tonight it is 26 outside and temps in the pens are at 32. Last year instead of lighting I used 30 gallon rubbermaid totes with 3X2 inch ventilation holes, two at the top and one at the bottom. On semi cold nites the birds stayed toasty with their own body heat, when it dropped below 10 I brought them onto the porch and stacked them. When I let them out in the morning I always checked their feet to see if they got a chill and they were always warm, no frostbite ever. The birds are easy to get down from the perches of a night with only 5 you could use two totes and put them in an enclosed area with no drafts and their own body heat should keep them warm. Make sure you keep fresh wood shavings or straw in the bottom because they poop of a night, though they seem to do it less when they are cold. Note that on some of my chickens through the winter all I had to do was put the totes out and they would go in them on their own, but i had to have a few with bigger hole.
You may want to consider dubbing your roosters to cut down on frostbite considering how cold Montana is. And maybe put heat tape under the perch so they could absorb the heat directly into their feet. That still probably would not stop the frostbite on the combs though. Also you should feed the chickens as much as they want to eat just before they go roost. They tend to stay warmer with a full belly for the night.
