This eSATA adapter now seems to work on the Mac. So you need to download the latest drivers from http://www.rosewill.com/products/d_814/productDetail.htm
Rosewill RC-605 problems | Tongfamily Website
I got this Rosewill eSATA so I could plug fast drives into my MacBook Pro. Well, like lots of third party stuff it doesnÃĸâŦâĸt really work. It is faster though, but you can only plug one drive in