We also have to understand that underlying all of what Romans is telling us is with a counter to obtaining righteousness by what we do, or works righteousness. That's not God's righteousness and it will not do. The Jews had replaced seeking God and His righteousness, with keeping traditions and Man-made rituals and although they may look good to some, they can not produce the kind of righteousness that God requires to justify a sinner..
Romans 4:5 - And to the one who does not work but believes in Him who justifies the ungodly, his faith is counted as righteousness.
Only God can provide the righteousness that the ungodly (all of humanity) needs in order to be declared just, not guilty, in His sight. We have to always remember that God was under no obligation to provide us with the rescue He gave us in Christ. We need to always thank God for His plan of salvation.
Another point that we need to focus on is Abraham's life not just His profession of faith. Abraham's life is what we need to see. We all talk about having Abraham faith as if it is a one time thing, I believed and its done, I have handled my spiritual business and now I can go about living my life as I choose. That is the deadly lie that shadows true, biblical Christianity. Abraham lived many many years before he had the son of promise, Isaac. Abraham walked in a walk that showed He truly believed God as Romans 4:20-21 shows: No distrust made him waver concerning the promise of God, but he grew strong in his faith as he gave glory to God, fully convinced that God was able to do what He had promised.
True faith in God requires the pursuit of a godly life, and just as Abraham faltered along the way, he did not stop his pursuit of a godly life. If Abraham is our example, we too must strive in our pursuit of a godly life, we have the same resources as Abraham, indeed, we have better than he, for we have what he was looking forward to, Christ. We look back to that, but we have the whole Word of God, available to us to read about how God dealt with people like Abraham and others.
Let us use all that God has given to us. All the means of Grace that lead us to obedience - just as Abraham was lead to obedience.