Here's an M5 file with the XM Roady's "power" IR command and the 10 presets. Unfortunately, the Roady remote uses a parity bit, so that's all the commands that can be effectively used with the MX-500. Maybe others in the same boat will find the file useful.
This works for all functions on the original remote. The codes from the built in database are used whenever possible and macros are used elsewhere to get around the toggle bit situation.