Congratulations on the find - here are the two posts I made on my recent Rogue acquisition (been on my list for years).
These two posts describe the drag and function in detail.
viewtopic.php?f=4&t=67897#p417147viewtopic.php?f=4&t=67897&start=25#p417295I looked at mine, the handle is definitely a rivet.
It's almost exactly the same length as a Medalist knob, the base of the knob is 0.05" larger diameter.
With the broken grasp, you'd be able to get a good measurement on the spindle diameter.
A One-Pfoot type Medalist grasp repair would be prime, but it's going to depend on that post diameter.
Any repair that would let you keep the post would also be choice.
We need to know the spindle diameter, but it might be possible to cut, drill and plug-tap for a 2-mm machine screw, and make a baitcast-type knob repair.
Esoteric, but a desirable result. The trick for this, it has to be a 4-mm spindle diameter.
(might also also be possible with 5 mm spindle)
Anything else requires drilling out the rivet, and here's Mike's reel repair answer for a new post and knob to go with an empty hole in the spool.
https://www.mikesreelrepair.com/black-h ... els-large/