We don’t see a lot of the Prince in the play. He represents law and order and makes several pronouncements during the play on the state of affairs regarding the feud between the Montagues and the Capulets. Although he tries to keep things under control, the relationships between the fighting families and Romeo and Juliet are too volatile to contain.
You could look at the Prince’s role as the counterweight to the emotional nature of what is going on in just about every other part of the play. If he is the voice of reason and order, the others are the voices of passion and impetuous action. While the Prince proves unable to contain the other characters, by the time all of the action has concluded itself, he is actually in charge of things and in a position to say “I told you so,” although he doesn’t’ really say it.