This policy setting prevents clients from connecting to Mobile Broadband networks when the client is registered on a roaming provider network. If this policy setting is enabled all automatic and manual connection attempts to roaming provider networks are blocked until the client registers with the home provider network. If this policy setting is not configured or is disabled clients are allowed to connect to roaming provider Mobile Broadband networks.
Network\Windows Connection Manager
At least Windows Server 2012 Windows 8 or Windows RT