What's the dramatic irony in Act Two of Romeo and Juliet?

One example of dramatic irony in this part of the play is that by this point Romeo is totally in love with Juliet. He's long forgotten about Rosaline, and yet Mercutio and Benvolio tease him mercilessly about Rosaline.

Also during this same scene Juliet's nurse enters and the 'boys' tease her. They don't know that she's there to speak to Romeo about Juliet.