In the spinoff film, Mikkelsen portrays Galen Erso (father of Felicity Jones’s Jyn), a scientist who is forced by the Empire to help complete the Death Star project.
In his response, Mikkelsen is most likely referring to the Star Wars novel Catalyst, which is a prequel to Rogue One.
This is why his performance in the upcoming Rogue One: A Star Wars Story seems like a refreshing change-of-pace.
Rogue One gives Mikkelsen a chance to play a sympathetic character, as the earliest rumors about the movie suggested that Galen felt tremendous guilt over what he had done.