FWIW: It's pretty cheap/easy to add resistance to rollers with aluminum drums. Stick a bunch of rare earth magnets to a bar and position it close a roller. The more magnets and the closer, the more resistance. Search a bit and I'm sure you'll find examples on the web. For example, check this: http://www.bikeforums.net/showthread.php/669900-quiet-cheap-effective-DIY-magnetic-resistance-for-metal-rollers

Or this: http://www.youtube.com/watch?v=TGMh7y2fEOE

Get magnets on eBay or Amazon.