Roxie proved herself to be a very capable Gym Leader, defeating five of Ash's six Pokémon despite being at a disadvantage in terms of her party. She would occasionally perform a riff on her bass during the battle, and the crowd would chant her name. When she was defeated she happily congratulated Ash as the crowd cheered for his victory, and she presented him with his eighth and final Unova Badge, the Toxic Badge.
This listing is of Roxie's known Pokémon in the anime:
Koffing was the first Pokémon Roxie used against Ash in their Gym battle. She captured it while she was in Kanto, and it inspired her to assemble her rock band, "The Koffing". During the match, it defeated Ash's Boldore and Unfezant rather easily, but was later defeated by Leavanny.