Most slaves were barbarian captives, taken as a result of war and purchased by land and home owners at a 'vile price'. Due to their former freedom and independence they were anxious to break free of their masters and exact revenge for their current condition. Therefore, they had to be restricted lest their insurrections reduced the republic to the brink of destruction. At times in Rome there were a greater number of slave than free which did cause a fair amount of turmoil within the city.
A slaves condition within a Roman home was solely dependent upon the temper of the dominus - master. It was not uncommon for a dominus to carry out his wrath on the slave unto the point of near death or even death itself. This knowledge filtered up to the government who eventually ruled that they, not the home owner, had the responsibility for the life or death of the slave thus giving slaves more freedom.
Salves were forbidden to participate in government affairs for 3 to 4 generations from their capture but eventually they did move into the senate and other high positions of government.
Although they were forbidden to participate in government affairs, most notably the senate, they played important roles in the theater where they acted in ways which they would not be allowed to do in regular life. Since the southern part of Italy was heavily influenced by the customs of the Greeks, slaves were given more freedoms than that which was allowed by the Romans such as marrying, owning land, and borrowing money.
This, in a sense, opened the eyes of the Romans to customs of other lands thus enlightening their thinking. Even though they were barbaric they quickly adopted certain manners and customs of those whom they conquered thus making them wiser to the ways of the world.