The first "real" character to speak in Romeo and Juliet is Sampson, a Capulet servant who opens Act 1 Scene 1 with the line "Gregory, o' my word, we'll not carry coals."
Other than that, a voice was narrating the opening scene "Two households, both alike in dignity, In fair Verona, where we lay our scene, From ancient grudge break to new mutiny, Where civil blood makes civil hands unclean."