I just tested the version of ReBirth RB-338 available at http://www.rebirthmuseum.com/, and can verify it works flawlessly in Crossover Pro 7 on Slamd64 12.0/12.1 (CURRENT).
The only trick was a manual mapping of my drive letters in the bottle directory. It looks like this:
draeath@epicenter:~$ ls -lah .cxoffice/rebirth/dosdevices/
total 8.0K
drwxr-xr-x 2 draeath draeath 56 2008-06-26 00:07 ./
drwxr-xr-x 6 draeath draeath 4.0K 2008-06-26 00:07 ../
lrwxrwxrwx 1 draeath draeath 10 2008-06-25 23:57 c: -> ../drive_c/
lrwxrwxrwx 1 draeath draeath 16 2008-06-26 00:06 d: -> /media/RB338V20//
lrwxrwxrwx 1 draeath draeath 8 2008-06-26 00:07 d:: -> /dev/hdc
lrwxrwxrwx 1 draeath draeath 13 2008-06-25 23:57 y: -> /home/draeath/
lrwxrwxrwx 1 draeath draeath 1 2008-06-25 23:57 z: -> //
draeath@epicenter:~$
The trick was the 'd:' and 'd::' entries - that got the program to look in the right place for it's CD check. You could use the real CD, or use 'losetup' to map the ISO file to /dev/loop# and mount that, that works fine as well.