JOHN BROWN Model 115 taillight repair

[Skolzie]

I have a taillight that one of the round lens holders, has undergone some surgery. It appears that the rounded rim(which holds the lens in place) has been bent up to a straight position. See photo. I'm searching for a method to "re-roll" the metal to a rounded position to match the other two lens holders.
Thanks much for your help.

p.s. (can't make the photo attachment work)