What is a "Roger"? A device? Software?

See the term used here quite frequently.

It appears to be a Phonak technology to use remote microphones.

It’s a system that uses both receivers and remote microphones. the remote microphones are pretty sophisticated allowing either omnidirectional or directional usage. Their claim to fame is offering the best signal to noise ratio for speech in noise. If you Google Phonak Roger, you’ll find a ton of info. It has mainly been used in schools, but is gaining popularity.

It’s a really bad name.