Your /mnt/cdrom1 is probably the mount point for your CD if you mount a CD. That is established in /etc/fstab, where this mount point gets assigned a physical device, presumably /dev/cdrom1. You'll find that even that is a symlink to some actual device, /dev/scd0 in your case.
Your problem is, most likely, that the permissions for /dev/scd0 aren't set right in order for you (as a regular user) to make ioctl calls to it. Do (as root)
chmod 666 /dev/scd0
and try again.
Hope it helps,