Hi Joe,
We would be able to assist with Rockettheme templates but I really prefer that you guys contact them for their templates.
We will assist our users with their RT templates, but it would be as a last resort, meaning if RT are not available at all.
That being said, not being able to send mails (PHP Mail) is never a template related issue. It is always a server/site configuration issue.
You can set any other template as default (be it Gantry 5 based or not) and you will experience the same issue.
Just double check your site configuration under "Global Configuration" -> "Server" and if everything is fine there, contact your hosting support.
In very rare occasions, the issue might be caused by a 3rd party plugin that messes the things up, but I doubt it that this is the case with your installation.