Good news is Jesus Christ our Lord

Romans 1:1-7
The gospel he promised beforehand through his prophets in the Holy Scriptures regarding his Son, who as to his earthly life was a descendant of David. 
Through the Spirit of holiness was appointed the Son of God in power by his resurrection from the dead: Jesus Christ our Lord.
Through him we received grace and apostleship to call all the Gentiles to the obedience that comes from faith for his name’s sake. And you also are among those Gentiles who are called to belong to Jesus Christ.
What impelled Paul to write at this particular point we do not know. Perhaps he already sensed he was risking his life by going to Jerusalem, and felt he might never speak to the Roman Christians in person. So he sets out vital elements of the Christian message important for them in their current situation and to help them understand more about his teaching.
The great theme of Romans is faith in the death and resurrection of Christ as the only ground of acceptance by God - a God who treats all people alike, Jew and Gentile.
Paul pulls no punches in describing the state the world is in. Everyone stands condemned by God's standard. Even the Jew, who has the unique privilege of knowing God's law, cannot keep it. But God offers us free pardon and new life. What we cannot do for ourselves, Jesus has done for us. We are free to make a fresh start - this time with all the power of God at our disposal.
Why?
Through God's grace so we can know Him and accepted him for his name's sake.
Because of Paul's obedience to the Lord so we can accept the grace of God, not only Jews, all who believed in Jesus Christ could be Christians. 
It is not because what we have done, but because of what He has done.
How?
Jesus Christ is the only way to the Lord, for who he is but not whom I am.