If you do your research, you will find that, in the Roman empire, it was illegal do have sex with woman that the man was not married to. However, slaves, on the other hand, were a different matter. Slaves were not considered citizens and, as such, were considered property. Thus, one could do anything to slaves so long as the do'er owned the slaves. History accounts are replete with indications of just how deviated slave owners were. Any slave female was fair game for just about anything and, often, were depicted on Roman artworks.
But, yes, sex with boys was a common and expected activity -- boy citizen or boy slave alike. It was not considered bad but, rather, a social requirement. Christianity came alone and put an end to sex with boys but certainly not with female slaves. That, with young girls as young as infants up to young adults, continued for centuries after Rome fell.
I'm not selling you on the Romans. The museums are full of the facts of life back then. But you don't have to take my word for it. Go visit the museums and libraries yourself.