Preheat oven to 400 degrees F (200 degrees C). Line a baking sheet with parchment paper.
Lay puff pastry on the prepared baking sheet. Place a 4-inch bowl upside down in the center; mark a circle with a paring knife and make 4 cuts from the center to the edge of the marked circle, giving it a star-like shape. Remove bowl. Spread cranberry sauce around the center of the dough; top with Brie slices and pistachios.
Bring 1 point of the star and the outer edge of pastry inwards over the filling; press together. Repeat with other pieces of dough, until it resembles a wreath. Brush with beaten egg and sprinkle with rosemary.
Bake in the preheated oven until golden brown and Brie cheese has slightly melted, about 15 minutes. Remove from oven and let stand 5 minutes before serving.