Note: My asparagus was quite thick, and it took 10 minutes to roast, but I like mine still a bit crisp. If your asparagus is really skinny, or you like it a little more well done you may have to adjust the roasting time accordingly. Also, the bright lemon flavour really shines through in this recipe, so if you just want a hint of lemon instead, reduce the lemon juice/zest to half a lemon.