Current world leaders should look to the example of Rome's most peaceful emperor, Antonius Pius. Pius was unlike most Roman Emperors in that his reign was a relatively peaceful one for Rome. Peace is more likely to bear prosperity for citizens as opposed to nations that go to war. Therefore, leaders should strive for peaceful rule, like Pius did in Rome.
If we start looking that far back for leadership, it opens the door to saying that other things from the times, like slavery, should also come back. Yes, Pius was peaceful, but we have many more current leaders such as Martin Luther King Jr. that today's leaders can look to.
Augustus reshaped the Roman infrasctructure to accomodate the empire Rome had become and initiated an era of unprecedented trade, culture, and wealth. He fought wars when it was to Rome's benefit, yes, but overall he did far more to build Rome than Antonius. Antonius simply avoided wars because his predecessors had made them temporarily unnecessary. His rule was one of circumstance, not of conscious decisions.
Modern leaders should look for opportunities to lead peacefully in today's world. It is foolish to think they can lead the same way a Roman emperor did many years ago. The world is different and the challenges leaders face are different. Leaders must base their actions on the current environment.