I think perhaps you're confusing Roman history with some other period of human history, perhaps on a different continent. In the Roman empire there were slaves

I think perhaps you're confusing Roman history with some other period of human history, perhaps on a different continent. In the Roman empire there were slaves who taught philosophy, slaves who managed large estates, etcetera, and people could both sell themselves into slavery and be freed from slavery. In fact, selling oneself into slavery was a popular route to becoming a Roman citizen. If you don't want to read a history book, for which I wouldn't blame you, you might nevertheless enjoy Robert Harris's Cicero trilogy, which gives a fairly accurate impression of Roman society (or so claim many reviewers more competent than me). It's a truly amazing period of human history, when life was so modern in some ways, and yet so different from today in other ways, and the world was small enough for an individual to change the course of history.