If your Roku is connected to WiFi and you own a smartphone you could download the Roku app. However the Roku device must be connected to the same network as the smartphone. Otherwise you could get confused. I’d recommend a physical replacement remote like the RC-AL7 (Regular Voice Remote) or RC-S01 (Voice Remote Pro).
@Tivoburkee is knowledgeable with remotes of any kind and can help you more in this situation.
I’m into videotapes and old electronics stuff, including extenders, converters and analog 4:3 TV sets (which are obsolete these days), and Miss Bianca is my favorite character in Disney’s The Rescuers (1977) and its sequel, The Rescuers Down Under (1990). I am not a Roku employee, only a user like you. ~ Jordan