Same exact thing happened to me. I am dealing with it right now! You can replace just the roll arm. the new one will press on with some difficulty, in other words, a very tight fit! Clean off as much of the old glue as you can so it will go on easier. You can glue it back on if you want, but mine went on so tight that it didn't need any glue. Make sure the camera is on the correct side when you press it on. It is entirely possible to put it on the wrong side with the camera upside down if you're not paying attention and it is very difficult to remove again! (Ask me how I know this)!!!
At this moment, with it all back together, I have "no image transmission signal" and "gimbal disconnected" errors. I'm going to replace all of the ribbon cables to try and correct it. I'm not saying you will have those same errors, but I have them after just replacing the roll arm.
Good luck, take your time and handle everything gently.