What were the economical consequences of the Roman expansion in the Mediterranean Sea?

Before the Punic Wars, Rome had been a relatively small nation located on the Italian peninsula. It was primarily a land power. Economically, it was based on paid labor and small agricultural holdings. As part of the conflicts with Carthage, Rome gradually came to expand and transformed into an empire. 

The first major economic change resulting from this was the growth of trade and maritime power. Along with the benefits of trade came the import of foodstuffs, especially Egyptian grain, which caused a cycle of urban population growth, requiring an even higher volume of grain imports. This cycle was intensified by a change in the nature of Roman agriculture.

Partly as a result of imperial conquest, Roman agriculture expanded to include a vast estate called latifundia across the Mediterranean littoral, generally cultivated by slave labor. While these were more efficient than smaller plots, they led to a great concentration of wealth and income inequality. 

Roman conquests not only increased trade routes but also provided large numbers of slaves, something that contributed to economic expansion.