Innersloth released an update in November 2021 which included the addition of special roles with unique abilities. The Guardian Angel role was added during this update to allow players to interact more with the game even after they became a Ghost. I think it's wonderful that they included this diversity. The Engineer and Scientist roles are exclusive to Crewmates, the Shapeshifter role is exclusive to Impostors, and the Guardian Angel role is exclusive to Ghosts.