Rosier was a wizard and one of the earliest Death Eaters of Lord Voldemort. He was possibly the father of Evan Rosier or Felix Rosier. He fought in the First Wizarding War, and travelled to Hogsmeade in order to "wish good luck" to Tom Riddle in trying to get a teacher position at Hogwarts. It is possible that Rosier was deceased before the start of the Second Wizarding War; if he was not, he possibly fought at the Battle of Hogwarts and was presumably killed or imprisoned in Azkaban after Voldemort's final defeat.
First Wizarding War
Rosier fought in the First Wizarding War along with many other Death Eaters. He was also one of the Death Eaters who travelled to Hogsmeade, to say "good luck" to Voldemort, during his attempt to ask for work at Hogwarts, along with Nott, Mulciber, and Dolohov. It is possible that he was the father of Evan Rosier, who attended Hogwarts with Severus Snape in the 1970s, and who was killed by Aurors in the end of the First Wizarding War. After Voldemort's first downfall, Rosier was presumably killed, imprisoned, or defected. If he survived, it is most likely that he was one of the Death Eaters who did not search for Voldemort.
Second Wizarding War
It is unknown if Rosier was still alive during the Second Wizarding War; if he was, he possibly fought in several battles, including the Battle of Hogwarts. It is likely that after the war he was either killed or sent to Azkaban.
Behind the scenes
- It's possible that he is related to Druella Rosier, wife of Cygnus Black, given the timeline it's likely that the two are brother and sister or possibly cousins.
- Rosier was not mentioned in the guide to Lord Voldemort's Death Eaters on Pottermore.
- It's possible that he was one of the boys seen with Tom Riddle in Horace Slughorn's memory, though it is unconfirmed.
- Harry Potter and the Half-Blood Prince (Mentioned only)