how do I update list of trusted root certificate authorities

There must be a way to tell OSX to go out and update it's certificate authorities. Our campus has a valid trusted certificate for its Virtual Desktop Interface servers & all our windows machines verify the cert without even asking. Windows also updates root certificates regularly and way in the long past I have had to manually update certificate authorities on windows.

But OSX ElCap with all the latest mac updates reject the VDI cert and don't even give me the option to accept it and I have to Manually download it & tell the system to trust the root certificate authority involved.

Isn't there a way to tel ElCap to update its list of certificate authorities?? A cert update commandline??