The Roku app on a mobile device can only connect to Roku devices that are ALREADY connected to the local network to which the mobile device is connected. You cannot use the Roku app to interface with a Roku that isn't already connected to the local network.
To connect a Roku to a local net you'll need to have a remote compatible with your Roku. If you tell us the model of your Roku, someone here will be able to advise you of an appropriate remote.
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