RGBDOS is a patch for RSDOS to allow the use of virtual hard drives. I believe it was the only patch of it's kind ever created for RSDOS.
See: http://home.att.net/~robert.gault/Coco/Downloads/Downloads.htm for RGBDOS for emulation.
For OS-9 use the emudsk.dr driver and /h0 descriptor found in Jeff Vavasour's CoCo 3 emulator package. http://www.vavasour.ca/jeff/trs80.html#coco3
Just continue this thread if you have any further questions.