I don't know, and neither I, we nor Vintage Machinery seem to have any maintenance or parts manuals for any Rockwell, Rockwell International or Rockwell-Delta or Delta-Rockwell metal cutting lathe. However, the carriage rides on the top of the bed (the "V" front way and the flat of the rear way), not on any gears. The rack gear that runs along the underside of the front way is used to manually traverse the carriage along the bed. While it is possible that one could design a carriage lock that somehow locks the drive pinion to the rack, that isn't how it is done on most lathes. Also, using a toothed lock plate driven by the carriage lock bolt would serve to lock the carriage to the bed. But that design would of necessity result in the carriage moving left-right almost every time that you locked the bed.
We do have a 4-page brochure on a 10" Rockwell metal cutting lathe. Assuming that that is the machine family that you are referring to, I see in two photos what I assume is the square head of the carriage lock bolt on top of the right front saddle wing. In that location, it could lock a plate up under the rack teeth by this would be undesirable for several reasons. It probably locks a flat plate up under the front edge of the front way. If no one replies with the plate dimensions, you will need to determine how much space there is for the plate. I would guess that it will look similar to the one for the Atlas 10" and 12" machines. There is a dimensioned photograph of that one in Downloads. Look for Atlas 9-14 Carriage Lock Photo.