In the Baptist church my father taught classes on Romans and almost every debate we've had theologically has had to do with the exegesis of that book. But tonight my friend and I who have a bible study decided to go into it.
I was able to teach the Catholic doctrine of justification by infused grace through faith and the doctrine of initial justification by faith alone, and progressive justification by God's grace and our cooperation/acceptance of it. I enjoyed sharing the differences in terminology (ie. Justice is God giving you what you deserve, Mercy is God not giving you what you deserve/punishment, Grace is God giving you something you don't deserve/gift), and teaching the non-imputation of sin and God's loving forbearance, and how it is contrasted with the Judaizer's doctrine of salvation by works/pelagianism.
It's always wonderful for people to learn that we don't have to try to work to God, he has come to us, we must only let him in. (to use some Baptist language).
As well I noticed verses about the "obedience of Faith" which Zwingli & the Anabaptists talked about and showed how it countered Anti-Nomianism. So with the condemnation of Pelagianism and Anti-nomianism as well as the Augustinian doctrine of justification by God's infused grace through an obedient/loving faith, we went through Romans 1-4. It's always a joy to do Romans, a beautiful epistle. I also used Luther's preface to his commentary on the epistle to the Romans to explain how the one seeking works will find only frustration, and the one seeking faith and works will likewise fail, but to the one who trusts in God will come faith and works and love. I'm glad that I'm able to use Zwingli and Luther's teachings (partially) to explain the proper Catholic doctrine.
"since all have sinned and fall short of the glory of God; they are now justified by his grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a sacrifice of atonement by his blood, effective through faith. He did this to show his righteousness, because in his divine forbearance he had passed over the sins previously committed; it was to prove at the present time that he himself is righteous and that he justifies the one who has faith in Jesus...Do we then overthrow the law by this faith? By no means! On the contrary, we uphold the law." - Romans 3:23-26,31
In Catholicism, it's Christ merit and superabundant grace (via the Holy Spirit, or the Sacraments, inside or outside the Church), accepted in faith leading to love and obedience (works), all of which are a part of the process of justification, by which we mean being declared just and being made just, lost by mortal sin, regained through perfect contrition and repentance, or the sacrament of reconciliation. (the 'difficult gospel', not easily slogan-ized. Although Papa Benny has called it "justification by love alone")