Dozens of languages could be heard on the streets. Rome's expansion turned the city and other parts of the Empire into a cosmopolitan and multicultural place.

In the provinces, elements of Roman culture were regularly adopted. People learned Latin and Greek far away from Italy and Greece in order to better adopt the ways of the Romans. Roman dress, architecture, technology, games, and religion were practiced throughout the Empire, often blending with local practices.

All this being said, for much of Roman history, Latin culture, as well as Greek culture to a large extent, were the dominant cultures of the Empire. The Patrician class was made up of native Romans and representation in the governing bodies heavily favored those descended from the original Latin tribes.

Roman expansion and especially the Roman conquest of the eastern Mediterranean changed the character of Roman political power. Having to participate in ongoing warfare and often sacrifice their lives for the republic was an enormous burden on Roman peasants. Meanwhile, the aristocracy accumulated most of the benefits that the expansion brought; they acquired new wealth, slaves, and social contacts. An extensive network of patron-client relationships developed between Roman senatorial families and wealthy provincials. Other group benefiting from Roman conquests were enterprising, middle-class knights, who served as state contractors or tax farmers; the latter robbed the provincial populations, earning hatred and resentment.

Aristocrats used Rome’s new resources to appropriate public land in Italy and, whenever possible, to force their peasant neighbors to cede their land to them. Where the peasants had maintained small farms, the aristocrats created vast estates run largely by slaves and devoted primarily to animal husbandry. Small groups of the more civic-minded members of the Roman elite, such as the Gracchi brothers, perceived the disposession of the Roman peasantry as a direct threat to the stability and integrity of Roman political system. They attempted to reverse the tide of mass impoverishment and rural depopulation, but the aristocratic majority party (the optimates) opposed them and murdered the Gracchi and some of their supporters.

When the dynamic Roman general Marius became consul, he dealt with the challenge of a dwindling supply of peasant army recruits by creating a new, professional army that was loyal to its commanders rather than to the Republican government. This, in turn, led to the civil wars of the 1st century B.C.E. and the collapse of Roman republic.

The expansion of the Roman empire led to the Pax Romana, a 200-year period of relative peace that followed the consolidation of Roman power. The Romans ruled what was at that time an enormous empire of 70 million people. They built a system of roads throughout their lands and established a strong military presence in their territories. This allowed people to travel long distances safely and thus led to a growth in commerce and cultural exchange. It also led to Rome accumulating vast wealth. Not only did the Romans borrow heavily from Greek culture, which they greatly admired, they were able to support learning, a leisure class, and the arts throughout the empire and to build or appropriate vast libraries. At the time of its final fall, the Roman empire was so intellectually advanced that it would take more than a 1,000 years for Europe to begin to surpass it. 

The Pax Romana eased the spread of Christianity because of the relative safety of travel in the empire, as well as the use of Greek as a common language. Even as the empire came under increasing threat, at which point Christianity was adopted by Emperor Constantine, the vast learning in the empire allowed Constantine to assemble the best minds in the world to hash out a sophisticated Christian theology in various councils, such as the Nicene. This had an influence within the empire and thereafter. Gibbon, who wrote The Decline and Fall of the Roman Empire, contended that the cultural impact of Christianity undermined the empire.

The impact of the expanded empire has been vigorously debated, but some scholars contend that it led to high income inequality and debt peonage to a point that these factors undermined the empire and weakened it from within. 

The expansion of Roman power throughout the Mediterranean affected many aspects of political life.

Conquests meant enslavement of many conquered people, thus expanding the role of slavery in the Roman economy and contributing to the growth of large estates (latifundia) and possibly to economic inequality as well.

Roman became far richer by her conquests, acquiring most importantly a secure grain supply from the enormously fertile Nile region of Egypt.

Rome’s conquest of Greece by force of arms led to an influx of Greek culture into Rome, transforming Roman literature, rhetoric, and art to reflect Greek models.