How does Romeo's character change in Act 1, scene 5 of Romeo and Juliet?
Up until this point, Romeo has been mooning around, suffering from unrequited love (or lust) for Rosaline. His father is worried about him, because he wanders around at night and stays in his room by day. His friend Benvolio persuades Romeo to go in disguise to the rival Capulet family ball, saying there will many beautiful ladies there to take his mind off of Rosaline. Romeo says that won't work, and he will never find anyone to replace Rosaline, but agrees to go anyway.
At the ball, in Act I, scene 5, Romeo meets Juliet and instantly falls in love, forgetting all about Rosaline. He changes from a moping, lovesick creature pining for Rosaline to a young man overjoyed, on top of the world, and ecstatic to have found Juliet.