There is Craigslist of course and PadMapper (though their listings are bit thin)--they used to be best way of finding a pad because they map out the locations better than Craigslist. I don't think there is a magic bullet for finding a place though. You might try googling "sublet rockridge". There are also websites like Roomster (though I just checked and they have nothing in Rockridge). It's a bit of a hassle. Good luck.
You might even try walking around Rockridge a bit--sometimes they will put a "For Rent" sign even before they try listing it.
