Disconnect all the Minis and work on the Roamio first. Connect the MoCa bridge to your router and then setup the Roamio to use MoCa only mode. Make sure all the lights on yourMoCa bridge are lit solid. If they're not unplug both the bridge and the Roamio and then plug them back in. Once those lights are solid then you should have a good MoCa connection. Start adding the Minis back one by one.
Also you don't have FIOS do you? Because their routers already have MoCa built in, so that could be causing interference with what you're trying to do. If you do have FIOS then you shouldn't need the MoCa bridge.
Developer for VideoReDo