What roles are played by Friar Laurence and the Nurse in Act 2, Scenes 3-4 in Romeo and Juliet?

In Act III, Scenes 3 and 4 of Shakespeare's "Romeo and Juliet" both Friar Laurence and the Nurse are catalysts to the tragic fates of Romeo and Juliet and others, as well.  For, had they not become complicitous in Romeo's plans, the marriage would not have taken place, at least not with such celerity.  Then, too, Romeo would not have told Tybalt that he loved him in the street when the young man is so distempered if he had not married Juliet.  Without Romeo's remark which incensed Tybalt, Mercutio and he may have just continued to bandy words and not have drawn swords.

The duplicity of the Nurse and Friar Laurence is most unexemplary, as well.  Both adults are in positions in which they should wisely advise the young people to respect their parents. Yet, Friar Laurence, especially, steps outside the bonds of his station in life when he agrees through subterfuge to marry the young couple.  For, he is a friar, one of an order that takes the vow of humility.  On the contrary, his act of surreptitiously marrying Romeo and Juliet without the consent of the parents is one of overweening pride:  Friar Laurence believes his act will effect a solution to the feuding of the families.  However, in his arrogance, he is wrong; in fact, he is the most responsible for the death of the two young lovers.

Similarly, the Nurse forgets her position of maturity and immerses herself giddily in subterfuge.  Shortly after Juliet is married, Lady Capulet urges her daughter to marry Paris. Aghast after her mother leaves, Juliet seeks comfort from the Nurse; instead the Nurse tells her to marry Paris, knowing that Juliet cannot do this. Unwisely, she advises Juliet to marry Paris, saying,

Faith, here it is,/Romeo is banished, and all the world to nothing/That he dares ne'er come back to challenge you;/Or if he do, it needs must be by stealth. (III,v,214-216)

Her words, suggesting bigamy, upset poor Juliet so much that the young woman contemplates suicide, and later turns to Friar Laurence, becoming a part of his desperate plan to reconcile the families.  However, his "best laid plans"  do not work as his message does not reach Romeo before he enters the tomb and discovers Juliet as she lies "dead."  Impetuously, Romeo takes the poison and dies in the arms of his young wife.  Truly,the poor judgment of the Nurse and Friar Laurence serve only to ignite the fire of the impetuosity of the two star-crossed lovers, Romeo and Juliet.