Marion, I do the following to root my roses: I like to take the cutting from a branch that has had a bloom that has just finished blooming. I cut it so that I will have 2 sections of leaves, then I cut the spent bloom off the top. I put the cutting immediately into water while I get more cuttings, prepare the soil, etc. I like to use few drops of a product called "Super Thrive" in the water I soak it in, and in the water for the dirt. I use miracle grow potting soil in a small container. I get it wet, but not so much that it will be sitting in a puddle. I make a hole in the dirt with a pencil. I take the rose out of the water, and make a few shallow cuts at the base, then I dip it in Schultz TakeRoot powdered rooting hormone, and stick it in the hole in the dirt. I put the little pot of dirt and rose into a zip lock bag (I like the 2 gallon ones) then I zip it most of the way up, and blow air into it to create a mini greenhouse. I put it in a window that does not get direct sun. In my case, a north facing window. I don't touch it for at least 2 weeks, then I lightly pull on the stem to see if it has rooted. If the stem turns black, it is dead. If it grows mold, it needs to be cleaned off immediately or thrown away so that it doesn't effect the other cuttings. If you are successful, in 2-4 weeks new leafs will start to grow. If you used clear cups for the dirt, you will start to see white roots in the soil. I adapted my method from this video I watched when I first started: https://www.youtube.com/watch?v=LiL83eUKWY8

If it's going into an attached garage, just throw it out there. You'll find elaborate instructions for getting plants ready to change circumstances, but I've never had anything bothered by moving that isn't a ficus. Plants go in, out, into below freezing temperatures, into hot, dry houses - they don't care. Now the coldest my garage ever gets, is low 20's F. And that's with -20°F and serious wind chill. Below freezing is relatively normal, but it has a hard time getting much colder than that. The roses in the garage have started to leaf out. I need to start watching them, and get them outside fairly soon. My current problem is that there isn't anywhere to put them that isn't covered with snow and isn't in the direct path of cars. I have to at least find the back walk before they can come out. During the spring, they do a fair amount of moving in and out depending on the weather. Our current forecast is for above freezing temperature until Wednesday night, so they could definitely go out for a couple of days. If the forecast low is below around 28°F, or I have reason to believe it is going to get colder than that, they have to get moved back in for the night. If a cold spell comes, and they have to spend a couple of days inside, they just have to. The strange thing, at least IMHO, is that while they start growing so much earlier than the in the ground roses, they don't tend to start blooming that much earlier. Mutabilis has a very hard time beating R. hugonis, and it should be working with a several week head start. There is a definite learning curve with this.

If you carefully dig and pot them once you're confident they are well-rooted, they'll be mobile enough to move in or out of protected environs as necessary when winter comes. If you have an unheated, insulated garage you might keep them there during the worst weather, or you could bury the plants on their sides in the garden until spring. The latter method is very easy and relatively foolproof, but I recommend finding a spot with good drainage for this purpose. Good luck!

I'd try the jars myself. When they lose their leaves if they do, I'd cover them with jars and leaves, then remove them in the spring. I have a few like that now covered with jars, but I started them with jars because I ran out of pop bottles. As long as the one is still green, I don't want to deprive it of light, don't think the others look like they are going to make it, leaves cooked off but stems still green on some. I'm not peeking. If it warms up too much, since they haven't been under jars, they could cook, so I'd watch that carefully, or do like one lady's method, rinse the jars with a little muddy water to diffuse bright sunlight. Congratulations on getting some rooted that way. I tried that with some extra cuttings, and they were the first to flop. Maybe like the other poster said they are hardy and will survive in situ as is.