What was the main purpose of the book of Romans?
Romans was written to show that every person is a hell-bound, filthy, wicked sinner, whether or not they committed listed sins, and then to present the remedy: the Gospel. Christ has already forgiven, died, and paid the payment by His blood; the only required response is to believe it.
Les explains that the whole idea of the letter to the Romans was to show that we were nothing but hell-bound, filthy, wicked sinners—every one of us—whether we actually did any of the things listed or not. Potentially, we were all capable of going to the very depths of sin. That is what Romans shows us. He then says the remedy is the Gospel: Christ has already forgiven us, already died for us, and His blood has already paid the payment. All we have to do to appropriate it is believe it. Les calls Romans very doctrinal and basic, in contrast to the problems in Corinthians and the legalism in Galatians.