Ubuntu doesn't set a root user account password (youo can't log in as root through the normal login process). Your first user account will be in the group adm and/or admin, and can use sudo. If you need an interactive shell from the root user, use
If you need to execute a specific command as root, use
The biggest down-side I find with this setup is that using sudo with re-direction doesn't work as one might hope because the shell evaluates the suso, then tries to re-direct the results in the original [user priv] shell. This is usually OK, but when you want to re-direct to a file that onoly root can modify, it's a problem. You can get around it like this:
sudo bash -c 'echo "only root can write here" > /onlyroot'