In this recently-released image from The Crimes of Grindelwald, Grindelwald is shown accompanied by Vinda Rosier, one of his supporters. The name should sound familiar to Harry Potter fans, since she shares last name of several minor characters in the original series, all of which have some connection to Voldemort.
Vinda Rosier and Leta Lestrange both seem to be Grindelwald supporters, which in a way is surprising, because Deathly Hallows makes it sound like Grindelwald was never powerful in Britain. It makes sense for some British wizards and witches to think he has the right idea, but his army should be mainly Durmstrang and Beaubatons graduates, not previous generations of Slytherin/Death Eater families.
However, Grindelwald is sort of a precursor to Voldemort. Their goals and methods are slightly different, but they are united in their belief that wizards are superior to muggles and that “pure-blood” wizards are superior to muggle-borns. In that way, it makes sense that a few of the ancestors of the Death Eaters would be drawn to Grindelwald just as their descendants are later drawn to Voldemort.
Which brings me back to the Rosiers. Although they’re not a prominent Death Eater family like the Malfoys or Lestranges, they’re woven into so much of the backstory that they were almost certainly important in a behind-the-scenes way.
Tom Riddle Jr. was born December 31, 1926, not long after the events of the first Fantastic Beasts movie. At this point, he’s a very young child growing up in a muggle orphanage. Therefore, the unnamed Rosier who was one of his school peers would also be an infant or be born very soon. Could Vinda be his mother? If so, then he would grow up surrounded by Grindelwald supporters and longing for the day when he, too, could fight for them. At school, he meets Tom Riddle, a classmate with ideas very much like what he’s heard at home. Grindelwald is defeated in 1945, around the time Tom Riddle and his classmates leave Hogwarts, leaving a power vacuum he’s all too happy to fill. Rosier, as the child of a Grindelwald supporter, would have no love for Dumbledore and most likely a desire for vengeance. He becomes one of the first Death Eaters.
Evan Rosier, presumably the older Rosier’s son, went to Hogwarts at the same time as Snape, and they were part of “a gang of Slytherins who nearly all turned out to be Death Eaters”. Therefore, Evan Rosier was one of the bad influences that led Snape to become a Death Eater himself. He died during the first war against Voldemort, killed by an Auror while trying to avoid capture. Said Auror is implied to be Mad-Eye Moody, who mentions that Rosier “took a bit of me with him”. Although Evan Rosier died before Sorcerer’s Stone begins and is never really developed as a character, he definitely made an impact through his interactions with Snape and Moody.
But it doesn’t end there. Let’s assume that Vinda is Druella Rosier’s mother as well. Druella Rosier grows up much like her unnamed brother, surrounded by pro-Grindelwald sentiment, and in the aftermath of Grindelwald’s defeat, marries Cygnus Black.
When Sirius describes his family to Harry, he says that his parents were never Death Eaters. It’s not that they were against the Death Eaters, per se, but they weren’t about running around in masks and killing people. They were content to cheer from the sidelines. However, Druella’s mother was not, and neither is her brother. We don’t know if Druella was ever a Death Eater or an active Grindelwald supporter, but she definitely had relatives who were, and she might very well have, much like Bellatrix, dreamed of sending her own children to fight for the Dark Lord. Fierce, ruthless Bellatrix would have wholeheartedly embraced the role. Knowing that the Lestranges were another old family of Death Eaters and Grindelwald supporters, I can see her seeking out Rhodolphus Lestrange as a husband, not out of love but as a way to get into Voldemort’s inner circle. Before long, the whole extended family is working for Voldemort.
Now here’s the interesting thing: the Rosiers and Lestranges were longtime Death Eater families, but the Malfoys weren’t, nor is there any sign yet that they were involved with Grindelwald. Older generations of Malfoys come across as more like Sirius’ parents, utterly despicable but uninvolved, and Draco’s grandfather even seems to have been an old friend of the stubbornly neutral Professor Slughorn. I tend to imagine Lucius Malfoy as a first generation Death Eater who joined well after Voldemort’s rise to power began. Snape, Barty Crouch Jr., and Igor Karkaroff would also fall into this general category. These newer recruits typically lack the fierce loyalty of the ones born into Voldemort’s service and were drawn in by promises of greatness but unwilling to go to prison for him once he was gone. They would likely have been recruited by in-laws or classmates, and in the case of Lucius Malfoy, that would be his wife’s family.
And Regulus Black? His parents weren’t Death Eaters, but they had the same kind of twisted morals. He was the youngest of the family, and as he was growing up, his cousins would have already been getting more and more entangled with Voldemort. It wouldn’t have taken much for one of them to whisper in his ear that this is the way to save the family’s honor after Sirius and Andromeda’s betrayals. And he would have believed it, because everything Voldemort did was in line with his parents’ beliefs, if not their actions.
There’s no way of knowing yet if Vinda Rosier is directly related any of these people. Maybe she’s an aunt or a distant cousin instead. Maybe Rosier is her maiden name and she marries into a different family. Maybe she dies childless and has no impact on the main Harry Potter story at all. But it would be an odd choice to give Grindelwald a supporter from an important Death Eater family and not expect there to be some connection. Leta Lestrange can’t be Bellatrix’s ancestor, because Bellatrix is a Lestrange only by marriage, but Vinda Rosier can, and it makes a lot of sense that she would be.
Almost all the high-profile Death Eaters from the main Harry Potter series can be traced back either to the Rosier and Lestrange families or to Tom Riddle’s original group of “friends”, which included members of both families. Now we know that the Rosiers and Lestranges were Grindelwald supporters before they joined Voldemort. While the two had different goals and methods, Voldemort did not just emerge to fill the power vacuum left by Grindelwald but in fact inherited his supporters as well.