ROM is Range of Motion. You want to keep your range of motion as you get older. If not, the body stiffens up and you can't move.
I saw the following video.
It reminded me of when ROM exercises became active. That meant I would do them. I'd use my good arm to move my bad arm. Before I did that, ROM was passive. A nurse or aide routinely moved my limbs.
Use your good arm to move the other.
I saw this:
