1) Radio frequency control is usually proprietary. There is no such thing as a universal controller for RF products. 2) Your URC remote broadcasts on 433MHz narrow band. Roku and NVidia Shield use WiFi frequencies (2.4GHz).
Your MX-990 controls products by Infrared (IR). Either emitting the IR directly from the front of the remote or by transmitting the data RF to the base station, where it is emitted thru the IR ports on the base station to the equipment.
The Roku has an IR receiver for responding to regular IR commands. So either you program your MX-990 to control the Roku directly. Or thru the MRF-350 by sticking one of the IR emitters on the Roku, from one of the 6 IR ports on the MRF-350.
The NVidia shield is a little more complicated. Depending on your model, it may have an IR receiver built in. Or if it has no IR receiver, then you have to get an IR dongle to plug into the NVidia USB port to control it via IR.
