Here is my cdrom mount line from /etc/fstab
/dev/hdc /media/cdrom0 udf,iso9660 user,noauto 0 0
So if you see anything with iso9660, that is your cd/dvdrom. In this case I have an IDE hard drive, so it is hda, and the cdrom is hdc. On a machine with sata drives and 2 DVD roms, it looks like this:
/dev/hda /media/cdrom0 udf,iso9660 user,noauto 0 0
/dev/hdb /media/cdrom1 udf,iso9660 user,noauto 0 0
Except for very unusual hardware setups, it will always be between /dev/hda and /dev/hdd.