I've just discovered the roku remote appIn an emergency, you can download a TV remote app for the phone. I was amazed at this, it does work (with a wifi-connected TV, anyway). Didn’t change the actual remote, with a broken button, for ages! - but a physical remote is still better than the app.
I am endlessly annoyed when the remote is missing and everyone 'searches' for it within 10 inches of their vicinity i.e. not getting off their arses!