Juice 2 oranges, 2 limes and 1 lemon to measure approximately 1/2 cup of juice. Combine the citrus juices and the sugar in a saucepan and warm over medium heat until the sugar is dissolved. Cool.
Thinly slice the remaining orange, lime and lemon.
In a large pitcher, combine the ice, citrus slices, raspberries, vodka and Limoncello and stir.
Top with Prosecco; stir gently and serve; garnish with fruit if desired.