Balthasar brings the news of Juliet's death to Romeo. In Act V, Scene 1, Balthasar says to Romeo, "Her body sleeps in Capel's monument / And her immortal part with angels lives." (V.1.19-20) He also tells Romeo that he saw the funeral procession and recognized some of the Capulet servants there. Romeo is devastated upon hearing this news, and he immediately decides to return to Verona to see Juliet one last time before he dies beside her.
It is important to note that Balthasar also mentions that he tried to send a letter to Romeo, but it failed to reach him due to the quarantine imposed on Mantua. This information highlights the impact of external events on the tragic outcome of the play. If Romeo had received the letter, he would have known that Juliet was only in a deep sleep and not actually dead, and the tragic ending might have been avoided.
Overall, Balthasar's news is a turning point in the play and sets the tragic end in motion. Romeo's intense love for Juliet and his inability to imagine life without her are the primary reasons for his decision to end his own life, even though it leads to an inevitable and tragic end for both of them.