Well, I still say the term "Cruiser" is best defined as any motorcycle with a feet-forward riding position, and that the term "Roadster" in today's motorcycle jargon mainly refers to a motorcycle with a more standard-style riding position, much as the RocketIII "Roadster", the short-lived H-D Street Rod which was based on the V-Rod, the V-Max, the BKing....and yes, this Ducati.
(...in short, the Diavel is NOT a "Cruiser", and mainly because of how one would position themselves on it in order to ride it.)