The nurse’s use of the word “ropery” suggests to Romeo another word which is an apt description of Mercutio: rope-ripe. It refers to someone who speaks too much and uses overly elaborate language. (It jokingly stems from the fact that this type of person is so irritating that they are fit to be hung.)  Romeo implies that Mercutio will speak more in a minute than he will “stand to” in a month.