How to enable Ubuntu root account
Ubuntu is one of a few distribution what came with root root account disable. What they are doing that? Because they are sustain a good security policy and anyway you will don’t need the root password to do administrative tasks on your desktop. You can use sudo to do that and for sudo (if is configured right) you will need just your account password. I also encourage all people to work with sudo and don’t use directly the root password.
Anyway to enable the root account just run:
sudo passwd root
And enter the password twice.
Good Luck !