Welcome to the forum.
Is there a particular fault with either of the machines, as normally you wouldn't need to update the firmware, as this usually only happens when you change boards and such.
As with all machines there is no way to backup the firmware, but you may be able to upload an older version.
The firmware for the EGX-600, that is at www.rolanddga.com
is the latest version and www.rolanddg.com
does not feature the firmware for engravers.
Normally you would contact you local service department for the firmware.