The beginning of Act I, sc. i, of The Tragedy of Romeo and Juliet begins with a street brawl between the members of the House of Montague and the House of Capulet. Prince Escalus warns both Lord Capulet and Lord Montague that the next time there is a fight between the memebers of either household, they will pay with their livees.
Lady Montague is worried, as his her husband, were Romeo was during the fray. They are concerneed, as is his friend Benvolio, that Romeo has been depressed; Lord and Lady Montague ask Benvolio if he can try and find out what's been bothering their son.
Benvolio has a conversation with Romeo in which Romeo confides his love for Rosaline. Unfortunately for Rome, Rosaline is a woman who does not return his affections and has taken a vow of chastity. Benvolio encourages Romeo to forget about her and look for another woman to love to no avail; Romeo remains despondent over his love for Rosaline.
In Act I, sc. ii, Romeo's friends learn of the "old accustomed feast" Lord Capulet is hosting that evening in his house when they run into Peter, a Capulet servant who is sent to invite the guest on the list. He asks the Montague boys to read the list for him. Romeo goes only when he learn Rosaline is invited to the party, a masquerade.
It appears that Romeo just wants to be in love with someone who returns that love.
Act I, sc. IV, on the way to the masquerade, Romeo reveals a bad dream, an omen that the evening's events will lead to death.
Act I, sc. V, is the moment that Romeo lays eyes on Juliet for the first time and instantly forgets all about Rosaline. This time Romeo finds a young girl who returns his love and matches his intensity.