rockboot.bin should be copied to /dev/sda1 using a command like:
dd if=rockboot.bin of=/dev/sda1
But from your second question, it sounds like you have already done that.
error message -1 means that you don't have Rockbox itself installed.
If you're compiling yourself, then the following commands are needed:
[Choose your ipod, and then "N" for a normal build]
unzip rockbox.zip -d /mnt/ipod/
The "make zip" command creates the rockbox.zip archive, and this needs to be unzipped onto the FAT32 partition on your ipod. Alternatively, just download the very latest rockbox.zip for your player here:http://www.rockbox.org/cvs.shtml