The way death rigging works is that the creator of the setup gets to reveal a specific role after a certain turn has passed or choose when that specific role dies at a specific time.
Here is an example. A game mode starts during the day with a single baker being the only role revealed. Nighttime comes and no matter who the mafia kills that night, the baker gives their bread away and dies. Death rigging can also be used to rig a single role to be specific in a closed roles setup similar to the game modes played in sandbox. This will allow for specific roles to always be in the random role pick and for them to be rigged in the case they're over powered, such as cultist all dying after the third night.
These rigs are completely made by the maker of the setup, meaning that I'm not suggesting baker die night one or cultist die night three, but, anybody who joins the setup can see that it's "death rigged" and can also check in what ways it's death rigged.