That is a huge question. Here are some points to get you started. First, the Persians and Romans were world empires. They took over so many people groups that the needed a way to keep their empire in order. Second, they both had regionalized governments (for the lack of a better term). The Persians had satraps and the Romans have provincial governors. Third, as you can imagine, both people had to deal with the religious beliefs of conquered people. They were both very open to other people's beliefs. For example, the Persians allowed the Jews to rebuild their temple and the Roman rarely persecuted any group based on religion. That should get you started. Good Luck!