http://askubuntu.com/questions/469143/how-to-enable-ssh-root-access-on-ubuntu-14-04
Simply adding a password for root is not enough for Ubuntu 14.04 Server.
You also need to edit /etc/ssh/sshd_config
,
and comment out the following line:
PermitRootLogin without-password
Just below it, add the following line:
PermitRootLogin yes
Then restart SSH:
service ssh restart