Just catching up - poor chap that doesn't look good at all.Video of Story today he is walking like I have heard people describe egg bound hens walk.but I don’t see anything amiss with his vent. Maybe his leg or hip got tweaked?
As others have said, he does not seem to be lopsided in his walk so it doesn't look like a leg injury. However, it is worth checking the soles of his feet and feeling along both legs because if he had a bilateral injury he wouldn't limp because both sides would hurt.
But as others have said, I think it is more likely to be his back or his belly.
Have you felt his belly to see if it is swollen or hard?
Although the whole ascites thing is usually talked about with hens because of reproductive issues, but there are other causes of ascites which might affect a roo.
I agree that giving him something for pain would be good - it looks like he hurts somehow.
Poor guy!
On isolating him or not. I would probably let him stay with the others - unless we know he has a leg injury that needs 'rest' there isn't really a need to immobilize him. But given your worry about the roost, could you bring him in during the night so he wakes up inside?