What books does Rise of the Runelords reference? Which bestiaries and guides will I need to play it?
Off the top of my head, I think that the first two bestiaries, the core rulebook, and the advanced player's guide are the most obvious. There is a mechanic from the gamemaster's guide as well (in the Skinsaw Murders). While GMing, I've actually printed off copies of the monsters I expect to use in each session from the web (though I own copies of all three bestiaries, I like to keep the monsters on a clipboard).
You could, if you wished, refer to paizo's website for the requisite rules. If you've got a laptop, you don't need to have physical copies of the books with you.
Hope this helps.