I would suggest that using the
root user or obtaining a password for it isn't a great idea as it could lead to a significant security compromise.
However, setting up SSH access using keys isn't anywhere as difficult as it seems. You need to generate a keypair (public and private) on your system; and then put the public key on your colleague's system. That's it. There are many pages describing how to do this including this one: https://www.linuxshelltips.com/passwordless-ssh-login/