@mheber I’m connecting to ROS OpenVPN with self signed certificate from iPhone by using official app from Appstore. Needed to add CA certificate exported from ROS into iOS as @MickeyT mentioned, full trust on iOS system level is not needed in my case (maybe OpenVPN app asked me about certificate trust on first connect, I can’t recall).
Export and download CA certificate file from ROS and send it over AirDrop to iPhone and install it. Make sure that certificates used by ROS server side and one in .p12 used by OpenVPN client app are signed with same CA.