“Do I need two of these devices? I have cable internet set up (cable modem and a wifi router) in a second floor bedroom. My livingroom tv, with Roku 3 is on the first floor at the opposite end of the house. Should I be able to install one of these devices to a coax jack near the tv and then connect to my Roku from the MOCA adapter via Ethernet cable? Or would I need a second MOCA adapter upstairs near the cable modem and router? Just looking to get a wired internet hook up to the Roku, not to extend wifi. Thank you.”