Who were the major characteristics of the Pax Romana?
This is a great question. Let me start with the time span. The period known as the pax romana lasted approximately 200 years from the battle of Actium when Octavian defeated Anthony until the time of the Emperor Aurelius. In view of this the first and main character of the pax romana is the founder of it all, Octavian (Augustus). He ushered in an age of relative peace after many civil wars and a time of properity. For example, Augustus closed he gates of Janus to represent peace.
After Augustus there were a few other important figures that brought prosperity and peace to the Empire. For example, the Flavian emperors - Vespasian and Titus were good emperors. In addition, the emperors of the 100's added stability as well - Nerva, Trajan, Hadrian, Pius, and Aurelius. Just the longevity of these emperors shows that there was great stability. Edward Gibbon's the great historian of Rome called this time the most prosperpous in Roman history.