First, we will list all Pokemon Rangers references in the anime. Then, we will sort them:
Swimmer Katelyn on Route 220 is based on Lizabeth from Pokémon Ranger and the Temple of the Sea.
This will not count since Swimmer Katelyn appears in DPP, not any of Pokemon Rangers game.
Lizabeth makes a cameo appearance in Pokémon Diamond, Pearl, and Platinum on Route 220 as a Swimmer using Buizel, Medicham, and Seaking, all of which were Pokémon used during the Marina Underwater Pokémon Show. However, this Easter egg was not recognized by the translation team, who named her Katelyn.
Source for this
In the Japanese version of Pokémon Ranger: Guardian Signs, Rand has a line in which he notes that "someone said that dreams will someday become reality".
The "someone said that dreams will someday become reality" line holds a reference to the "Aim to Be a Pokémon Master" song. While Rand doesn't makes a cameo appearance in anime, he is the Area Ranger in Pokemon Ranger: Guardian Signs.
Green Guardian, Pokémon Ranger - Deoxys Crisis! Part 1 and Part 2, Pokémon Ranger and the Temple of the Sea, and Pokémon Ranger and the Kidnapped Riolu! Part 1 and Part 2 are based on Pokémon Ranger, with Solana playing a large role in the two Pokémon the Series: Ruby and Sapphire episodes and making a cameo in the movie and DP episodes, and Kellyn playing a large role in Pokémon the Series: Diamond and Pearl episodes. The plot of each is based on a mission from the games.
This is the one you're looking for. Like how Solana is the main character of Pokemon Ranger that made appearance in Battle Frontier, similarly Kellyn is the main male character from Pokémon Ranger: Shadows of Almia who made an appearance in Pokemon Diamond and Pearl series.
That's all of them according to Bulbapedia here. I searched for "Pokemon Ranger" in that article, and I have listed those above. However, there is one more I remember.
Ben made his main series debut in Pokémon Ranger: Heatran Rescue!, where he was assigned to bring a rare Heatran that knows Eruption to the National Park for its own safety.
Ben is the main character in Pokemon Guardian Signs.
Ben is the male playable character in Pokémon Ranger: Guardian Signs.
So, we can conclude that from this that Solana, Kellyn and Ben are the only characters from Pokemon Ranger spin-off series that appeared in anime. However, except from some references non-main characters from those games haven't appeared in anime, according to Bulbapedia.
Hope this helps!