It's still early days for Guardians of the Galaxy 3, so nothing has been confirmed yet in terms of cast. However, it seems highly likely that Bradley Cooper will return as the voice of Rocket Raccoon. He's been a key part of the franchise so far and is one of its most popular characters, so it would make sense for him to come back.
We'll have to wait and see what happens though. If Cooper isn't able to return for whatever reason, there are other options available. The studio could recast the role or simply use existing recordings of Cooper's voice from the previous two films. Either way, we're sure they'll do whatever it takes to keep Rocket on screen for Guardians 3.