Bring 2 cups water, 2/3 cup sugar and 6 rosemary sprigs to a boil in a saucepan, stirring to dissolve the sugar. Remove from the heat and let sit 20 minutes, then strain. Refrigerate the syrup until cool. For each drink, combine 12 ounces cold wheat beer, 2 ounces of the rosemary syrup and 1 ounce each grapefruit juice and lemon juice. Garnish with grapefruit wedges and rosemary.