In the final act of the play, we see Balthasar deliver the news to Romeo that Juliet has died. The lines Balthasar delivers to portray the news have an ounce of irony in them. When Romeo asks how Juliet is and says that "nothing can be ill if she be well," Balthasar ironically replies, "Then she is well, and nothing can be ill" and goes on to explain that she has died (V.i.16-17). The irony in this statement is that because she is dead, Romeo will not think that she is well; however, because she is dead she can also never be ill again because she can never suffer again through sorrow or sickness. Therefore, Balthasar speaks ironic truth when he describes Juliet's death as being "well."
Romeo's reaction to the news is to curse the stars. It is also ironic that Romeo had just had a dream about Juliet waking him from the dead with a kiss that he took to be a good omen. Now it seems to Romeo that fate has tricked him. Fate has also surprised him by taking Juliet's life, when earlier in the play he believed that he would die young as a result of crashing the Capulet's ball. Hence, he shouts out, "Is it e'en so? Then I defy you, stars!" (24), meaning that he is going to try and challenge fate. If fate wants to take Juliet's life and leave him alive, then he is going to challenge fate's decision by taking his own life in his hand. Hence, Romeo's response to Balthasar's news is to decide to commit suicide in Juliet's tomb, by her side.