Help getting started with Roku devices, including setup, connecting your device to your TV, linking a Roku device to your account at my.roku.com/link, adding channels, subscribing to services, and more.
Re: how to hook up a nintendo switch and a roku express to a tv with one HDMI input
Hopefully they are just "playing it safe". For example, I've been on several support forums where companies will tell you to plug their USB device directly into a computer - not into a USB hub. Yet I plug them into a hub, and they work fine. I can understand that support people want to keep the variables limited and don't want to be blamed for a possibly flaky product in the middle.
That said, I know nothing of this device, and can't guarantee that they didn't do something "clever".