The story about your roo is so sweet, he is a very pretty boy, and in perfect health. It is so nice of you to take him in. I can
tell that he has really taken to you and just loves you. I agree with the other posters, you need to worry more about predators than
the cold. Chickens are outdoor animals and are built for it. Put your focus into making or getting him a secure place to sleep at night.
If you have a garage you could even put him there at night till you get something more perm for him.
What a nice looking boy you have there! He is very handsome and I would be so proud to have such a great rooster. That is wonderful of you to take him in as you did. I know he is so grateful to have a home.
I do also want to warn you that Rhode Island Red roosters have a reputation for sometimes being very aggressive about guarding their ladies. Take away the ladies and there is nothing to guard, sometimes.
But every rooster is an INDIVIDUAL and he may keep being a wonderful pet for you. I do indeed caution you to not quite think of him as a pet that you can trust.
Never place your eyes near him (as in letting him sit on your shoulder and you turn to look at him), nor allow a child to be near him with you not around (and if it is a small child, don't even let the roo get near in my opinion) as roosters and small children don't mix too well due to the unpredicatability of the roosters.
You didn't mention if you have children, but I thought I'd mention it since you are new to chickens. Welcome to BYC!
and I hope you can get him a nice flock of at least 8-10 ladies to prevent bare backs (I have seen this happen before and there is raw/bleeding skin involved) as he will tread on them with his claws when he mates. I once only had 5 ladies with one roo and that was a major problem.
The easiest coop to maintain in my opinion is a shed coop. Sooooo easy to deal with and you can view the coop section on here to get ideas. You can get a regular shed and make some changes to it on the inside/pop door added, and there you go!
Or if you are very cost/time conscious right now, you can see that many have posted their ideas with free and recycled materials.
OK....here's the updated version of Bach since he is looking healthier! The video is terrible quality...you have to put it full screen to really see him.... Santa is bringing me a new camera as this one is crap, so it's the best I have for now. Notice how he shakes his tail side to side LOL! He's such a showoff! He is off on his morning stroll right now, so I'll try to get some close up stills when he gets back. Maybe the pics will be more clear.