From Bulbapedia, the community-driven Pokémon encyclopedia.
Rosebay (Japanese: ユカリ Yukari) is a Pokémornithologist, and a character of the day who appeared in A Staravia is Born!.
Rosebay acted as a sort of Pokémon Ranger. Her job was to keep track of all of the Pokémon inhabiting a forest that Ash and his friends happened to be passing through on their way to Oreburgh City. She introduced herself to them and Brock quickly flirted with her before being dragged away by his Croagunk. Rosebay then invited the group along on her hike to look for Flying-type Pokémon. She first took them to a Swablu nest and noticed that the Swablu were gone, which prompted her to recall that a lot of Flying Pokémon had been going missing recently.
It was soon discovered that Team Rocket had set up a giant net in a gorge to trap the Flying Pokémon. Ash's Starly helped rescue the Pokémon, evolving into Staravia and defeating Team Rocket in the process. Rosebay thanked Staravia for his help and told Ash and his friends that the Pokémon were safe once more.
In the dub, Rosebay speaks in an English accent.