Antithesis: The lines beginning "With love's light wings did I o'erperch these walls, for stony limits cannot hold love out..." use contrasts (light/heavy, walls/wings, can't/can) to highlight the lovers' ability to overcome obstacles.
Oxymoron: The phrase "cold fire" is an oxymoron, expressing the paradox of Juliet's beauty both warming him with passion and freezing him with dread.
Alliteration: The repetition of "s" sounds in "soft, smooth, and slow" emphasizes the gentle and slow motion of the speaker.
Hyperbole: Romeo's exclamation "I am fortune's fool" shows his deep desperation and sense of being toyed with by fate, exaggerating his suffering and placing blame on an abstract concept.