I agree that you should treat the footrot first, certainly in the ewes. The old rams will probably not be edible other than in pies or as pet food, so if they are that bad you might be as well to call in the knacker to kill them humanely on the spot.
For the ewes, as well as trimming and a footbath with, say, Golden Hoof (zinc sulphate) once a week for 3 weeks, you can also give them an injection of long acting Terramycin. Once their feet are better and with some decent feeding, you may well find that their condition picks up to the extent that the ewes will be wonderful for sausages in the early summer. What are their teeth like? You don't say what breed they are, or why they had to be rescued.
If you keep other sheep, hopefully you are keeping these animals separate.