Mikrotik OVPN server and PFSENSE clients

HELP REQUIRED !!! - Is this possible ? I have a need to replace a pfsense OVPN server with a mikroitk RB3011 however the current clients are also pfsense boxes. I need to be able to setup an ovpn server to communicate with the existing pfsense boxes. All attemtps so far have failed. I can setup OVPN server on RB3011 but am unsure as to the correct setup of the server settings - do i need a ca and a key file ? and can i import the key and ca to the pfsense box.
The current pfsense clients have CA=no but are installed with a private key. has anybody done this ?