are you connecting the dvdrom device through usb or some other external plug? it will not be mounted as dev/cdrom it will be mounted as /dev/sdxy where x is a letter between a and c and y is a number between 1-6 usually sda- mounted devices are Internal drives sdb's and sdc's are external i would recommend setting teh device to find as /dev/sdb1 and if that doesnt work try /dev/sdb2 and if not either