He did not address those with "hostility towards God" as saints... ever.
Rom 8
4 so that the requirement of the Law might be fulfilled in us, who do not walk according to the flesh but according to the Spirit. 5 For those who are according to the flesh set their minds on the things of the flesh, but those who are according to the Spirit, the things of the Spirit. 6 For the mind set on the flesh is death, but the mind set on the Spirit is life and peace, 7 because the mind set on the flesh is hostile toward God; for it does not subject itself to the law of God, for it is not even able to do so, 8 and those who are in the flesh cannot please God.9 However, you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. But if anyone does not have the Spirit of Christ, he does not belong to Him.
Paul had no way to make sure that an unsaved church member in Corinth would never read his letter -- as we all know.
His letter was written to the Christian church at Corinth and certainly some of them were saved.
Meanwhile -- Back to the letter to the Romans. Chapter 8
Rom 8
4 so that the requirement of the Law might be fulfilled in us, who do not walk according to the flesh but according to the Spirit. 5 For those who are according to the flesh set their minds on the things of the flesh, but those who are according to the Spirit, the things of the Spirit. 6 For the mind set on the flesh is death, but the mind set on the Spirit is life and peace, 7 because the mind set on the flesh is hostile toward God; for it does not subject itself to the law of God, for it is not even able to do so, 8 and those who are in the flesh cannot please God.9 However, you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. But if anyone does not have the Spirit of Christ, he does not belong to Him.
Those who are "hostile" toward God... who do not subject themselves to the Law of God "neither indeed CAN they" -- are lost and in need of the Gospel.