The falling action of Shakespeare's Romeo and Juliet, as in any other play, is determined by the climax of the play.
Most scholars agree that the climax of Romeo and Juliet occurs when Romeo kills Tybalt in act 3, scene 1. This is a major turning point in the play and in the lives of Romeo and Juliet. Romeo is banished from Verona, and goes to Mantua. Juliet must contend with Romeo's banishment, the death of her cousin, Tybalt, and her parents' insistence that she marry Paris.
From this point in the play, all of the major conflicts of the play start to be resolved, which is the falling action of the play.
Friar Laurence devises a plan by which Juliet will avoid having to marry Paris, and Romeo and Juliet will be reunited.
Friar Laurence gives Juliet a potion that will cause her to appear to be dead, and that she'll be buried in the Capulet's tomb. After forty-two hours, Juliet will recover from the potion, and Romeo will be there to take her from her tomb and to Mantua.
In the meantime, Friar Laurence will send a letter to Romeo telling him about the plan, so that Romeo can come back to Verona, rescue Juliet from the tomb after Juliet recovers from the potion, and return with her to Mantua so they can spend the rest of their lives together.
Juliet performs her part of the plan flawlessly, but Romeo doesn't receives Friar Laurence's letter, which causes serious complications for Romeo and Juliet.
This leads to the resolution (or denouement) of the play. Romeo returns to Verona to Juliet's tomb too early, finds Juliet still apparently dead, and Romeo kills himself. Juliet recovers from the potion, finds Romeo dead beside her, and kills herself.
Some scholars contend that the climax of Romeo and Juliet occurs when Romeo and Juliet kill themselves in act 5, scene 3.
The falling action includes the finding of Romeo and Juliet already dead, and Friar Laurence's explanation of the unfortunate events that led to Romeo and Juliet's deaths. Friar Laurence, the Prince, the Capulets, and the Montagues all blame themselves for Romeo and Juliet's deaths.
The resolution of the play is the Montague and Capulet's decision to end their feud.