The drink I am referring to was always freshly made - the hotel where we stayed in Rome served the common juices (orange, grapefruit) as a matter of course, but if you asked the server real nicely, they'd go into the kitchen and would have someone whip up the "supreme." Now I wish that I had followed the server into the kitchen and watched the process.
The drink was also available in cafes (where they'd charge about 6 euros for it).
I don't have any blood oranges now, but I figured I'd do the research now and be prepared when I see them back in the stores (ususally around Nov/Dec I think). I didn't realize that it would be so hard to figure it out.
Thanks for your help!