As many people know Ubuntu distribution come default with the Root account not accessible. For most all of your needs that require Root you can use the sudo cmd.
But, If you are wanting to be able to access the root account you need to be able to set the password. This is very simple to do.
1. Log into your server or desktop via SSH or just use your shell if you are currently at the computer.
2. Type this command
sudo passwd root
You will be prompted two times for a password. Thats it.
Now to log into root via SSH you would log into to the box normal then type the command su root and then type the password.
Remember to SU back so you don't make any mistakes and loose your whole system.