Rosier (I)

Rosier was a pure-blood wizard from the influential Rosier Family and one of Tom Marvolo Riddle's earliest followers at Hogwarts School of Witchcraft and Wizardry. As a member of Slytherin House during the 1940s, he was part of the group of students who would become the first Death Eaters. His primary significance lies in his presence during Riddle's inquiries into the nature of Horcruxes, marking him as a foundational member of Lord Voldemort's inner circle. He is the presumed father of the Death Eater Evan Rosier.

Rosier attended Hogwarts in the 1940s and was sorted into Slytherin House. During his time at school, he became a member of Tom Riddle's gang of acolytes, a group of ambitious Slytherin students who shared Riddle's interest in the Dark Arts and pure-blood supremacy. This group included the forefathers of other prominent Death Eater families, such as Avery (I), Lestrange (I), Nott (I), and Mulciber (I). In a memory Albus Dumbledore showed to Harry Potter, Rosier was present at a Slug Club meeting where a sixteen-year-old Tom Riddle questioned Professor Horace Slughorn about Horcruxes. Rosier and the others listened intently as Riddle probed Slughorn for information on the possibility of creating more than one Horcrux, a pivotal moment in Riddle's path to becoming Lord Voldemort.

Rosier's activities after leaving Hogwarts and during the First Wizarding War are not documented in the primary canon. It is known that his son, Evan Rosier, became an active and notorious Death Eater who was killed by Aurors near the end of the war. The fate of Rosier (I) himself—whether he was an active Death Eater, was imprisoned, or died before or during the conflict—remains unknown.

Rosier's physical appearance is never described in the books. When Harry Potter witnesses him in Professor Slughorn's memory, no distinguishing features are noted. Based on his association with Tom Riddle's circle, Rosier was likely arrogant, ambitious, and cruel. The group was described as a collection of Riddle's “friends,” though their dynamic was more that of followers to a leader. His presence during the discussion of Horcruxes indicates a deep-seated interest in the most dangerous forms of Dark Magic.

While no specific magical feats are attributed to Rosier, his inclusion in Tom Riddle's elite group suggests he was a capable and talented wizard. Membership in this circle, which formed the nucleus of the Death Eaters, was likely reserved for those with considerable magical aptitude and a strong affinity for the Dark Arts.

No specific possessions belonging to Rosier are mentioned in the novels. As a wizard, he would have owned a wand.

• Evan Rosier (Presumed Son): Evan Rosier was a prominent Death Eater who fought in the First Wizarding War and was killed by Auror Alastor Moody after a fierce duel. The use of “(I)” to denote the elder Rosier suggests a direct father-son relationship.
• Rosier Family: The Rosiers are a very old and wealthy pure-blood family, recognized as one of the “Sacred Twenty-Eight” pure-blood lines (Pottermore).
• Druella Rosier: A relative, possibly his sister or cousin, who married Cygnus Black III and became the mother of Bellatrix Lestrange, Andromeda Tonks, and Narcissa Malfoy. This connects the Rosier Family to the Black Family, the Lestrange Family, and the Malfoy Family by marriage.

• Lord Voldemort: Rosier was one of the first followers of Tom Riddle, showing loyalty and deference to him from their school days.
• Original Death Eaters: He was a close associate of Avery (I), Lestrange (I), Mulciber (I), and Nott (I), forming the core of what would become Voldemort's army.

• The surname Rosier is of French origin, meaning “rose bush.” In demonology, Rosier is the name of a fallen angel who became a demon of love and seduction. This dark connotation aligns with the character's allegiance to Lord Voldemort and the alluring, corrupting nature of the Dark Arts.

• Rosier's first name is never stated in the seven canonical books.
• The Rosier family's history of associating with Dark Wizards predates Voldemort. In the The Crimes of Grindelwald film, a witch named Vinda Rosier is a loyal and high-ranking follower of Gellert Grindelwald (film).
• The list of the “Sacred Twenty-Eight” pure-blood families, which includes the Rosiers, was published by J.K. Rowling on the Pottermore website (Pottermore).