whipwarrior: Laserschwert is right. There's no actual "CD-ROM version". The only CD-ROM releases of Monkey Island two were compilations which featured the floppy version. I've been collecting various versions of these games for years, and I can tell you that Monkey Island 2 is about the easiest, as there is only one PC version. All subsequent releases are copies of the original floppy version. I just checked my White Label Double Pack CD, and the files are the same as my original floppy version.
Monkey Island 1 has a version with CD audio, and this would be included in the compilation CDs. Monkey 2 uses iMuse and never had CD audio.