When the play begins, Romeo is infatuated with Rosaline and mourns her indifference. She never actually appears onstage, but she is spoken about at length in the play’s opening scenes. The audience knows very little about Rosaline—only that she is very beautiful, and has sworn to live a life of chastity.
Rosaline is an essential character, despite her lack of presence within the play. To begin with, Rosaline’s rejection of Romeo is the catalyst that sets the entire plot in motion because Benvolio, Mercutio, and Romeo crash the Capulet party to take Romeo’s mind off of Rosaline. Furthermore, Romeo’s many tangents about Rosaline at the start of the text are crucial for his characterization; they establish that Romeo is an impulsive, passionate young man who feels things very deeply. One can learn a lot about Romeo by comparing his love for Rosaline with his love for Juliet. Romeo is a great reader of love poetry, and the play’s depiction of his love for Rosaline suggests he is trying to recreate the feelings that he has read about. However, it appears to be more of a surface-level love than anything of substance, proving that he is more in love with the idea of being in love with Rosaline than he is with Rosaline herself. Unsurprisingly, Romeo forgets about Rosaline the moment that he sees Juliet, highlighting the superficiality of his previous sentiments. Romeo may initially see Juliet as a heroine from a love poem (Juliet even tells him that he “kiss[es] by th’ book”), but his feelings quickly develop into a deep, authentic love (1.5.107). It is important that the audience sees Romeo’s superficial pining for Rosaline at the start of the play because it renders Romeo’s star-defying love for Juliet all the more true, and therefore tragic.