Why is romeo so sad in act 1 scene1 of and Juliet?

In Act 1, Scene 1 of Romeo and Juliet, Romeo is not explicitly portrayed as being sad. Instead, he appears lovesick and preoccupied with his unrequited love for Rosaline, a woman who is not interested in him. Romeo's sadness primarily emerges in subsequent scenes as the plot unfolds, particularly after he meets Juliet and their love story takes a tragic turn.