Acid_kewpie is right; the cdrom entry in /dev is just a symlink to the actual device. Just do
The output will tell you, among other things, what device the link points to (hdc on my box). That information is only true if you haven't physically moved devices around on your IDE channels, of course. CD-ROM drives follow the same device-labelling convention as IDE hard drives: primary master= hda, primary slave= hdb, etc. I think IDE CD burners are different because they work under SCSI emulation in Linux (hence the "ide-scsi" entry in /etc/lilo.conf).