If the ideal woman in Shakespeare's time was supposed to have skin as white as snow and smooth and blond hair, then her cheeks are probably going to have to be pink and rosy too. You've probably picked up the pattern by now. The more clichés the speaker piles on, the more we see what a silly way this is to compliment someone.
- Line 6: The speaker takes the standard image of rosy cheeks a step further here, pretending to be surprised that there aren't actually red and white roses in this woman's cheeks. When you put it like that, it makes the whole metaphor (i.e. "her cheeks are roses") sound pretty dumb.