County Paris is important to the play in that he serves as a contrast against Romeo to show us just exactly how young and still young-minded Juliet truly is. Paris represents Juliet's alternative more rational choice. Juliet does not actually have a genuine reason to prefer Romeo over Paris. Paris is equally handsome, possibly even more so, as we see from Lady Capulet's opinion that, "Verona's summer hath not such a flower," and the Nurse's agreement (I.iii.81). Paris is older, wiser, and has the higher noble rank of a Count, showing us that he can provide for her far more fully than Romeo ever could. Not only that, Paris genuinely loves Juliet, as we see from his persistence in asking for her hand and from his genuine grief over her faked death. However, Juliet allowed her young emotions to be swept away by Romeo simply because he was far more forward with her and even gave her her first kiss. Thus, Paris serves to represent adult, rational thought in contrast to Romeo, who represents youthful emotionalism.
Prince Escalus is very important to the play in that he represents the deep, booming voice of justice, law, and even of philosophy. He acts as the voice of law by laying down the harsh penalty of death should the two families battle in the streets of Verona again. He acts as the voice of justice by justly sentencing Romeo to banishment instead of death for killing Tybalt when he learned that Tybalt had started the quarrel and even slayed the prince's own kinsman, Mercutio. He frequently acts as the voice of philosophy by referring to Lord Capulet and Montague as "beasts" for spilling blood to "quench the fire of [their] pernicious rage" (I.i.80). He further acts as the voice of philosophy by showing us just how much damage Capulet's and Montague's feud caused. We see this in his lines in the closing scene,
See what a scourge is laid upon your hate,
That heaven finds means to kill your joys with love! (V.iii.301-304)
Without Prince Escalus's wisdom, the readers/viewers would not truly be able to pin hatred as the true cause for all of the death in the play.