There's a verbal contradiction, but it's easily harmonized. You might wonder, well, why does he begin his discussion with the second phase of salvation? Wouldn't logically he want to start with the first? Well, go back to the very beginning of Romans. Who does he address his letter to? It's to the saints who dwell in Rome. So he is addressing the letter to people who have already been saved. So they've already been saved. They need to worry now about the second phase of salvation.
So that's why he starts with that, the second phase that there will be a judgment based on works.