Mac OSX and enabling user root
Root login over SSH is not enabled by default for good reason.  Since you are not connecting remotely in your example, I recommend:

sudo su


to switch to root user if you need to run several commands in a row.  This keeps you from needing to do the much safer

sudo commandname


where you need to prefix every command with sudo. If ssh is a requirement, you can simply:

ssh user@host


and then

sudo su


to switch to root user. This is a much safer approach from a security standpoint. 

Lastly, if you really think you must enable root login over ssh, see this link for instructions.