A tropical cocktail of Vodka.
I tried to use Sherry to play a supporting role. Though "Roulette" has some bitterness, it probably derives from the flavor of grapefruit.
I think it may be good to add gum syrup according to your preference.
I used Amontillado (one type of Sherry) this time. When you use other Sherry ( Oloroso, Fino and so on), you might find other new taste. I used Absolut Vodka as usual.