Solana, Kellyn, Ben and Jack Walker are Pokémon Rangers that have appeared in the anime.
Many episodes have featured other rangers. They generally keep an eye on an area and look after the Pokémon there. Some of these areas are restricted and have to be protected from poachers. As these rangers train Pokémon normally, though, they may have more to do with the Trainer class than the Fiore and Almia Rangers.
Solana first appears in the The Green Guardian, and later in Pokémon Ranger - Deoxys Crisis! Parts One and Two, where she is involved in the incident with Deoxys. She appears again together with Kellyn in Pokémon Ranger and the Kidnapped Riolu! Parts One and Two.
Ben, the male protagonist from Guardian Signs, made appearances in the anime in SS022, SS023, and Pokémon Ranger! Heatran Rescue Mission!!.
Jack Walker is the central character of the ninth movie, Pokémon Ranger and the Temple of the Sea.