Augustine's soteriology has a lot in common with Roman Catholic soteriology. The main difference is that they recognize seven sacraments but he numbers fewer. He identifies baptism, penitence, and alms (for him, good works broadly considered) as the means for remission of moral sin, and private prayer as sufficient for the forgiveness of venial sins. The Roman Church would add to that Auricular Confession, which is a practice that arose later in church history after the Hibernian model of penitence, and the Mass. Augustine of course believe in the Lord's Supper as a means of grace but his theology of it differed and he didn't see it as atoning. What he has in common with the Roman Church is the general outline of baptism forgiving sins prior to it, and other sacraments being necessary for following sins. This of course does not reflect our understanding of justification, and he shares the same flawed exegesis of passages from Romans, Galatians, and Ephesians on the matter of justification by faith as the Roman Church has. For Augustine, justification is "from faith alone" because saving virtues (hope, love) come from a root of faith. But it's those works that actually save one as they are reckoned good in the judgment and one's deficiencies are removed by baptism and penitence, and compensated for with alms. On this matter there is a subtle difference between him and the Roman Church in that they use the language of "condign merit" for how man will be rewarded, and he attributes the reward to God's mercy, but the distinction is not enough to save him from charges of salvation by works. I prove quotes and citations for all of this
here.