That can be repaired fairly easily. Requires a bit of epoxy.
The shaft you see sticking out is PRESSED into the aluminum outer housing you see with the HOLE in it. Which now has even wollowed out and no longer will stay attached. Here is the issue. The shaft has to be EPOXIED, back into the hole, BUT, pay CLOSE ATTENTION, to the alignment, the shaft has to go in a certain direction, or roll will be off. First you need to align shaft with roll board ( requires taking small cover plate off ) see YouTube videos on correct shaft alignment. ) now place a TINY DAB, of epoxy in the hole, replace part onto shaft, keeping shaft perfectly aligned during dry time, prop something if you need to, tape, whatever, just keep it from moving until it completely dries. ( when I say a tiny dab, you don't need much, and you don't want it to ooze out onto any moving parts, ect. Next you'll need to replace gimbal ribbon cable, as yours was severed in two. Hint: start ribbon replacement at camera, and work twords main board. There are YouTube videos on all of this, please search around before you attempt repair. Hope this helps, and good luck.
You can just buy the replacement part, instead of repair, but I would try to repair first, and if all else fails, buy replacement roll arm.