root password required

I recommend for trivial issues (by trivial I mean issues you can easily find and answer/solution to by searching on this very same forum or any search engine) you use a search engine. searx.me is excellent IMHO.
That being said ->

sudo passwd root and enter the psswd for the root (make it complex and long passphrase)
su root to become root

Also changing network or any files in / you should be perfectly capable doing by using sudo. Hence no need to create a root account..
cheers

P.S - be aware that the first command sudo passwd root needs your normal (administrator account) password and then you need to enter the desired psswd for root..

The normal way to get administrative permissions on Trisquel is to be a regular user (well, a user in the 'sudo' group, such as the one created at install, unless you altered her privileges) and precede the administrative commands with 'sudo '. For instance, if you want to edit /etc/hosts with the Emacs editor, you execute:
$ sudo emacs /etc/hosts

The first time you use 'sudo' in a session, you will be asked for your password. Same thing if you have not used 'sudo' in the past fifteen minutes (configurable with 'sudo visudo'). If you really want the equivalent of a root terminal, execute this command:
$ sudo -i

Not having a root user by default (follow SuperTramp83's directions if you really want one) is a security feature. Take your SSH server as an example: the attacker not only needs to guess the passphrase but also the user's login. That eliminates the threat of script kiddies that try to log as "root" on every SSH server they can find.

jvn may have crashed headlong into the grub user trap, which asks for a username without saying that it is asking for the grub username, which is always (?) "grub." Given your own username, grub then asks for a password, again without specifying that it is the grub password, which is in that special place that Magic Banana never tires of describing, thank goodness.

This unpleasant minimization of textural descriptions dates back to the good old days of computing when everything had to fit on a floppy disk.

That said, whenever I have gone through a Trisquel installation, I have always been asked to give my desired username and password, which I have dutifully done.

Then Trisquel sometimes goes on to ask for a root password whenever root privileges are needed, but there is no need for any such root password, again as Magic Banana patiently explains, because one must instead prepend "sudo" before any such command in the console in order to gain root privileges [temporarily], or simply type one's own password when "authentication" is demanded in the GUI.

All that said, one is nevertheless allowed to add a root terminal to the Trisquel menu, which only compounds the confusion of the new or naive user.

Summary: You don't need to create a root password, and you shouldn't do that, ever, even when Trisquel asks.
The proper substitute is the use of the sudo modifier in console operations.