Someone had the bright idea of converting a Lamborghini Diablo into a convertible model, this was however never a factory built Roadster. The looks of this specific car were much like the Diablo SE 30 Anniversary edition, but with five-spoke multi-piece wheels mounted with 18 inch tires. The interior was a leather upholstered one with standard seats.
It is very unlikely this was a real Lamborghini, I personally think it was just a replica, modified into a roadster after a roll-over accident, just like the Countach Roadster featured on this site.
If it was actually a real Lamborghini built Diablo SE30, it was a very bad idea to convert it into an open-top car, the SE30 was only built at 150 units, with only 25 for the United States, so I can't imagine this conversion will force the price up, just like with the Miura, some cars were converted into roadsters but they never did get accepted by the true Lamborghini lovers.
A visitor to this site has mailed me the origins of this special Diablo, actually it started life as a normal Diablo VT, Platinum Motors have built this 'special' from it, probably to be able to sell it at a higher price than normal, according to this mail they are also responsible for the Twin Turbo versions of the Diablo, I suppose this is the Diablo VTTT found on a different page.