Romeo in Act 5 Scene 1 is officially banished. The scene starts with him having just had a dream where Juliet found him dead and kissed him back to life. (Shakespeare just loves giving you little hints about what's to come.) Romeo is thrilled with the dream:
If I may trust the flattering truth of sleep, My dreams presage some joyful news at hand: My bosom's lord sits lightly in his throne;
Ah me! how sweet is love itself possess'd, When but love's shadows are so rich in joy!
His joy is soon slapped back to reality when Balthasar visits him from Verona only to tell him that Juliet is dead. To ensure that Romeo understands that Juliet is dead, Balthasar admits that he saw Juliet's body being put in the family tomb.
Romeo gets very pale and wants to leave. He does pause for a moment to ask Balthasar whether or not he has a message from the Friar. Balthasar says no. Romeo then swings into planning his own suicide. He plans to die by buying poison from the Apothecary. His change in mood becomes almost desperate when he actually buys the poison. The Apothecary is not excited about selling the poison to Romeo but he needs the money.
Once Romeo has poison in hand, he is off to go die and be with Juliet in the tomb.
Romeo's tone is quite a bit darker post the news that Juliet is dead. He spins into almost Hamlet-esque imagery:
Art thou so bare and full of wretchedness,
And fear'st to die? Famine is in thy cheeks, Need and oppression starveth in thine eyes, Contempt and beggary hangs upon thy back; The world is not thy friend nor the world's law