Romeo is motivated by his interest in Juliet's looks. All he had to do was see Juliet and he forgot all about Rosaline, his love in Act I. Throughout the Act, Romeo's singluar purpose is to marry Juliet at whatever cost. He will keep the truth from his parents and sneak around behind his friends in order to make it happen.
The Friar is motivated to help these families come to some sort of agreement. He is tired of the feud and wants to help it be put to an end. Even though these kids are planning to marry in secret, he knows the truth will come out one day.
Juliet has a singular motivation for Romeo. Although she is encouraged to have interest in Paris, it is not happening for her. She envokes the use of the Nurse to try to communicate with Romeo about their wedding place and time.