I've taken the Atmel Studio FreeRTOS, created a new Rowley Crossworks Project, imported all the Atmel sources files, added a shed load of paths to included files and added the Chan Fat File source. I'm not sure whether this is really the right way to do it, but it certainly seems to work. The Atmel Studio version seem to have a load of header files in the project itself, whereas I've just given the project lots and lots of paths for user include directories.
I've created a thread that It will read the root directory of a 2G card and print it in the debug window of Ccrossstudio and another to flash the blue LED one a second. (You've got to have a flashing LED, obv!)
Hope this is of some help to other Crossworks users. :)