Change root password to be different than Admin password
I'm not sure I get what you want, but here's how things work on OS X.


You can't prevent an admin user from becoming root with their own password.
Root user isn't enabled, and doesn't even have a password unless you set one.


So, if you want to prevent a user from editing hosts, you need to remove their admin rights. Anything you can lock with special permissions, that admin user can unlock so what I'm guessing you ask is not possible.