I found Slaves and Masters in the Roman Empire: A Study in Social Control to be a tremendous resource for accurately building the relationships between the slave and free characters in my novel, Rubies of the Viper. Anybody who is interested in this subject will find this book useful.
Could slaves interact easily and openly with their owners? Were they educated? Smart? Moral? Loyal? The answer is: In many cases, yes.
Certainly, there were many slaves who were uneducated, disloyal, conniving, and self-serving. Many never met their owners, much less built a personal relationship with them. Many adults and children were abused--sexually, physically, and psychologically--on a regular basis. Many spent their entire lives in conditions that we today simply cannot imagine or believe.
But many Roman slaves managed their masters' estates competently and honestly. Many were true companions to their masters, often from childhood. Many served the same master loyally from birth to death.
But they were still property... and that fact was never far from their minds.
Every aspect of a Roman slave's life was 100% under the control of another person. The master determined what they ate and wore. What work they did, when, and how. What kinds of sexual relationships they could have.
A master's understanding of what he wanted from his slaves--total obedience and loyalty, in most cases--and his methods of getting what he wanted were perfected long before the first century A.D. They consisted primarily of what we would call the carrot and the stick.
The carrots: a tolerable life, decent food and living conditions, a semblance of family life, a chance to have their own savings and property (peculium), and a hope of manumisson
The sticks: corporal punishment, threats of being sold or sent to labor on a plantation, and even the possibility of death at the master's sole discretion