It's always best practice to disable root login over SSH, especially from the Internet; use su or sudo for root access. Another good practice is to disable password-based authentication; only use keys with a passphrase. The setup you're doing here is useful for allowing scripted/automated connections between machines (e.g. for backups, scheduled tasks, etc) but they should be accounts with limited access, not root. You should be creating layers that make it difficult for someone to gain access to your systems; root keys with no passphrase means you're solely relying on that one strong password (which is one keylogger away from being defeated.)
