He's a fictitious character who calls himself "Thad Bonjo", spoofing FM rock DJ's from the '70s. I've also heard "Thad" appear doing bits on the Loren & Wally show on the main station, must be someone on staff who does the character.
Except for the month before Christmas when WROR runs holiday music and they temporarily shift their main music mix to the HD2, that "Nothing But The '70s" format has otherwise been the same since I first got an HD radio five years ago. I like that it plays some songs that are rarely heard elsewhere anymore, but it's basically been the same loop of songs, TV themes and "Thad Bonjo" bits for about half a decade so far. I guess you just discovered it.