In a small sauce pot, heat the honey, rosemary sprigs, and 1/2 cup water until simmering. Remove from the heat, cover, and steep for 10 minutes. Discard the rosemary. This makes enough syrup for 4-6 drinks.
Fill a glass with ice. Add the grapefruit juice, lime juice, and 1-2 tablespoons of syrup. Stir to combine. Top with ginger beer. Garnish with grapefruit wedges and rosemary sprigs, as desired.
Notes
*To make a cocktail: Reduce the lime juice to 1/2 oz and add 1 1/2-2 oz vodka.