you dont actually need the -o ro flag, its implied with CDROM file systems (even loop mounts) as far as i am aware there is no cdrom FS wirting support in the kernel (it would however make making an ISO alot easier)
i have a half hight DVD burner/reader for my Z that i never use, but i was hhopping to watch DVDs on it using mplayer, i should really test that out
anyway it sounds like you might not have the correct module for your Z, i belive meanie has a compiled package somwhere