In a small saucepan over medium heat, combine 1/2 cup sugar with 1/2 cup water. Stir occasionally until sugar melts completely, then turn heat to a simmer and add in rosemary. Cook for 5 minutes, then remove from heat and allow rosemary to soak in sugar syrup for 30 minutes.
Place 1 cup of sugar into a small bowl. Remove the rosemary from the sugar syrup and dip each piece into the bowl. Shake off excess sugar and place on a cooling rack. Allow rosemary to set for at least 30 minutes more. To speed up process, place in freezer.
To make the prosecco cocktail, combine cranberry jam with orange zest. Spoon 1 teaspoon into each champagne flute. Pour a few ounces of prosecco and stir. Continue pouring until you almost reach the top of the glass, then top with candied rosemary!