Short answers, pulled from the story.
A slave in ancient Roman law lacked libertas, which is liberty defined as the absence of servitude. The common Latin word for slave was servus, but legally a slave was mancipium, meaning something taken in hand and subject to control.
Contubernium was a quasi-marital union between two slaves within the same household that had legal implications addressed by jurists. Although masters could break up families, evidence suggests that formation of family units was supported within larger urban households and rural estates.
Slaves were released from their master's control through the legal act of manumissio, with imperial household slaves routinely manumitted at ages 30 to 35. There were three kinds of legally binding manumission: by the rod, by the census, and by the terms of the owner's will.
The Jewish historian Josephus reports that the Great Jewish Revolt of AD 66 to 70 alone resulted in the enslavement of 97,000 people. The future emperor Vespasian sold 30,400 war captives from Tarichaea into slavery after executing those who were old or infirm.
As a matter of law Roman slaves could not own property but could be allowed to hold and manage property called peculium which ultimately belonged to their master. A fund set aside for a slave's use included profits from business transactions conducted by the slave and could include other slaves put at the disposal of the holder.