Romans 16:19 For your obedience is come abroad unto all men. I am glad therefore on your behalf: but yet I would have you wise unto that which is good, and simple concerning evil.
People are beginning to hear about the church at Rome. They are hearing about how they are living in obedience to what the Word of God says. Grace isn’t a license to not obey but rather the power and the desire to obey. It used to be written on stone tablets now it is written on our hearts.
Paul is proud of them. He is glad to hear that people talk about them and their faithfulness and obedience. But even in the moment he tells them that he reminds them to be simple, ignorant, unknowing about things of evil. We are to know about the good. We handle the good. Live the good. Love the good but the evil we just stay away from.
It is not a problem of being separated from evil but rather of being wise towards the good. Loving the good with all of our hearts and lives.