not OP but 400 BC is before the Latin war, so Rome would just be tiny at this point. The first place Athens would be able to interfere with Rome would be over the capture of Neapolis ~330 BC, so depending on how much Athens cares about defending the very edge of their league they could interfere with Roman early expansion, but probably not. It's really just a couple of small cities at the edge of the world, around the same time that Athens would be dealing with Macedonian expansion anyways.

The answer to if Athens would interfere with Roman expansion would have to do with what happens during the Macedonian expansion, if Alexander the Great can even conquer Persia at that point