The main subject is the revelation of God’s wrath against sin and of the only ground upon which a sinner can stand in righteousness before Him. Romans reveals what God has done with both sins and sin and how a Christian, as a saved sinner, is individually justified simply by his trust in the finished work of Jesus Christ.
Romans teaches that although a Christian’s sin nature continues to live within him in constant hostility to the “new man,” he can reckon the “old man” dead and walk in newness of life.
A Christian’s foundation for living in this fallen world is that he has been judged righteous in God’s sight, his salvation is permanent, and nothing can separate him from God’s love. Thus he sees that his human frailty does not invalidate what God has done for him and in him, and he refuses to spiral into despair when his sin nature gets the better of him.
Instead, he can be transformed by renewing his mind to the end that he functions as a unique member of the Body of Christ, showing by his words and works God’s abounding goodness and love.