With Moss Rose you don't even need a root..I have always just sat them in some dirt and covered a section..This will grow that way even if it is half dead LOL Water every other day for a week then once a week after that!
I live in a tropical area so it is always in bloom..but I had moved this last winter and 1 of them got left out in the freeze and I recently moved back to my warm/HOT climate and left my plant for my Sister, she said it has come back. I don't recommend leaving it out though..Maybe you can put it in a pot and keep indoors. ??? I sure hope this helps you!!!