To forward all root emails to a user you can add an entry in the aliases file, like:
root: sam
After updating the aliases run the command below.
newaliases /etc/aliases
Restart your mail server and you should see all root emails being sent to the user specified in the aliases file. A different process can be used to achieve the same behavior by making an entry in the .forward file of the root but I haven’t tried that as I prefer to have it done with aliases.