http://www.proaudiomusic.com/keyboards/roland/roland-u8.htm

The U-8 does seem to have some Mac compatability through a VST plug-in. I don't know what the plug-in is, or if it's available, or what, but it does seem to exist somewhere (or so this pages suggests).

You can look here, but I didn't see anything that screamed "ROLAND U-8 FOR THE MAC!" so good luck.