Paul is building an argument in Romans. Up to chapter 8 he wants the people of Rome to understand two points; first, we are all caught in the web of sin; second, that it doesn’t matter if we are Jewish or Gentile but we are all saved by faith. And, as Paul notes in chapter 8, it is faith in Jesus Christ that sets us free from the “law of sin and death.”
Paul wants his readers to understand this freedom. This letter comes later in his life. He has ministered all over the eastern Mediterranean and has seen people caught in the web and mindset of sin. Folks have faith, but forget that they live in this new reality of freedom in Christ. And this freedom means that we are children of God and His heirs. It is easy to skate over this idea because saying someone is a child of God has become a cliché. But it has deep meaning. As children of God we belong to God’s house. And in his house we have access to all that God provides and we share in his blessings. This does not mean we won’t suffer here, but it means that we cannot be separated from Jesus and the love of God.