In the opening chapters of Roman, Paul is at pains to show that the whole of mankind is unrighteous in the sight of God. "All have sinned and fall short of God's glory". The result of this is that the whole of humanity is condemned.
However, deliverance from this hopeless situation is possible through faith in Christ.
In this central section of Romans, Paul goes on to explain how the human react came under condemnation, not the grace of God operates and frees us form this condemnation, and how that grace operates in our lives today. In these chapters we are given an insight into the mind of God and the rational behind His plan for salvation.