William of Baskerville
William of Baskerville is an Oxford-educated monk and a follower of the scientist Roger Bacon (c. 1220–92) and the philosopher William of Occam (c. 1285–1347). He is devoted to acquiring knowledge. William seeks truth through signs and books and not through the torturous methods used by the Inquisition, which is why he abandoned his former role as inquisitor.
Adso of Melk
Adso of Melk is smart and curious and eager to learn logic, as well as wisdom, from his mentor. The novel is Adso's account of his experiences with William at the abbey. Adso writes the story as a memoir when he is an old man in the Melk monastery. As a youth he thought he'd learn that signs and words had true meaning and would lead to clear and definite answers to both questions and mysteries. But as an old man, Adso realizes it's not possible to discern order and meaning in the world.
Abo is proud of the abbey's great wealth in gems and precious metals, as well as in its renowned library. However, he is horrified at the prospect of scandal at the abbey and has invited William of Baskerville to discreetly investigate the disturbing deaths. The abbot wants the mysterious murders solved quietly so that the reputation of the abbey, and his reputation, are not tarnished.
Bernard Gui was a real inquisitor and persecutor of Franciscans who challenged the Church's wealth and power. Gui is ruthless in pursuing heretics and has no qualms about using torture to elicit confessions of heresy. He is sly as well as ambitious.
Jorge of Burgos
Jorge or Burgos is one of only two monks who understands the labyrinth and who has an encyclopedic knowledge of the books in the abbey library. He has been the real power behind the library and its secrets. Jorge believes laughter and comedy are sins, the work of the Devil, and he would rather see the great library destroyed than allow anyone to read the secret book on laughter secreted away in the hidden room.
Malachi of Hildesheim
As William and Adso discover late in the novel, Malachi of Hildesheim does not read Greek or Arabic. His ignorance puts him under the total control of Jorge of Burgos and, as instructed, he is highly protective of controversial books and manuscripts in the library, especially the secret book kept in the hidden room. Malachi has a homosexual affair with Berengar, which leaves him open to blackmail and scandal.
Severinus of Sankt Wendel
Like William, Severinus of Sankt Wendel possesses great intellectual curiosity. When he finds an Arabic text among some papers in the infirmary he tells William, who understands their importance to the secret book. But by the time William gets to the infirmary, Severinus has been murdered.