Rome had a strict class system based largely on placement at birth. Slaves could never be merchants and merchants seldom be aristocrats. Rome was generally tolerant of local religion and customs of the places that were conquered as a way to help integrate and assimilate the new citizens over time. These problems were exacerbated by continual, rapid expansion of the empire until it was simply too big to be governed, leading to the split of the empire between East and West, followed by their eventual fall.
