In a sauce pan dissolve the sugar in the water over medium heat.  It will take about 5 minutes.  Do not let it boil or it will turn to caramel. 

Once all the sugar has dissolved pour the mixture into a heat proof jar with the Rosemary springs.  Let steep for about 30 minutes to an hour.  

Chill in fridge until ready to use

In a cocktail shaker filled with ice combine vodka, grapefruit juice and Rosemary simple syrup.  Shake well.

Pour into ice filled cockatil glasses and garnish with rosemay spring.