[NorthwestGuy]

The router you are buying should set up a WiFi network and work as you want. I have setup simular configurations in my trailer. Keep in mind you need the devices to be in the same IP address range to communicate on the network. I have two WD boxes that are simular to your Roku, the simplest way is to load some movies on 64G thumb drives and plug it into the WD box usb port and access local source. This way I don't need a network at all. If you have a smart enough TV you can plug it right into a usb port on the TV and access the drive to play content. You can also connect with a smart tv over a network to the plex without the Roku. With the router you can access the internet with a computer or other device and send streamed content over your network as a bonus. Some Tv's let you "cast content from a device directly to the TV. My TV in the bedroom allows me to connect my tablet wirelessly to the TV and "cast" content to it(I think it was bluetooth). There are many ways to accomplish what you want these days as long as you can understand the capabilities and process.