What effect did Rome's expansion have on its economy?

Rome's expansion was both a blessing and a curse to its economy.  New lands brought under Roman control brought the Romans into contact with new goods and new markets.  Bread became cheaper as "softer" wheat from the Eastern part of the empire replaced the spelt that was commonly found in Italy.  This made flour easier to grind, thus making bread cheaper.  Other areas of the empire produced citrus fruits, fine metal products, and wine.  Rome was also able to assimilate technological innovations of conquered people as well.  

However, the expansion was a double-edged sword for Rome.  The roads connecting the empire required upkeep, and this meant taxation.  Also, the larger empire meant more land to protect from barbarians--again, this meant a greater tax burden as many of these assimilated people did not feel much loyalty to the government in Rome.  The Western empire fell into decadence as it soon produced little and consumed much compared to other parts of the empire--this is what led to the fall of the Western Empire.