Combine rosemary simple syrup, cranberry juice, lemon juice and gin in a cocktail shaker and shake over ice.
Strain into a Collins glass, add fresh ice and top with club soda.
Add one rosemary sprig and 2 to 3 fresh cranberries on a cocktail skewer as a garnish.
*Rosemary Syrup: Place1/2 cup sugar, 1/2 cup water and 5 rosemary sprigs in a pot. Bring to a boil, then reduce heat to low and let simmer for 10 minutes. Let the syrup cool. Strain to remove rosemary sprigs. Refrigerate for up to 3 weeks.