I ran INDI Control Panel, set the port to USB0, connected, and Saved the configuration (All from my Mac, the Focuser is connected to my Raspberry Pi). That created the required files. Hooray!
When I start indi_robo_focus, it complains that the RoboFocus_config.xml is missing from ~pi/.indi/
Can anyone provide a suggested one? Are the drivers documented somewhere?