Inspector
Receives the investigation results of all cops in the game, but does not know the identities of the cops or which investigations are by the same cop. Can choose any of the investigation reports to review, and this will reveal if the investigated person was a miller or framed by the mafia.
This role would be for a large game, with three cops: 1 sane, 1 insane and 1 naive. The inspector cannot review all their cases, and he cannot determine which investigations were by the same cop, meaning he cannot detect insanities without information from the cops themselves. There should also be a miller and a mafia framer in game, to further mess with the cop reads.