If you return a Pokémon recruited in Pokémon Champions to Roster Ranch, you will not be able to encounter that individual Pokémon again.
Pokémon that were sent to Pokémon Champions from Pokémon HOME can be sent back to Pokémon HOME and may be sent to visit Pokémon Champions again later. However, Pokémon recruited in Pokémon Champions cannot be sent to Pokémon HOME.