Romeo yearns for Rosaline, and despairs at her indifference toward him. Romeo’s Rosaline-induced histrionics seem rather juvenile. Rosaline, of course, slips from Romeo’s mind at first sight of Juliet. But Juliet is no mere replacement. The love she shares with Romeo is far deeper, more authentic and unique than “love” Romeo felt for Rosaline. Romeo’s love matures over time from the shallow desire to be in love to a profound and intense passion.
Romeo’s deep capacity for love is merely a part of his larger capacity for intense emotion of all kinds. There is a rather juvenility to his actions, and he seems to always act before thinking. In the movie, Romeo’s fighting style compared to Tybalts, and his jump to conclusions when told the gossip of Juliet’s death, are rather childish and driven by a strong emotion.