For the cocktail: 
Pour the bourbon, grapefruit juice, and simple syrup into a shaker. Fill with ice and shake 30 seconds, until frosty cold. Fill an old fashioned glass with ice, and strain the drink into the glass. Garnish with a cinnamon stick and a sprig of rosemary.

For the Honey-Cinnamon-Rosemary Simple Syrup:
Place the honey and water in a medium saucepan. Bring to a boil over medium-high heat, stirring until the honey has dissolved into the water. Add the rosemary and cinnamon, and turn the heat down to medium and simmer for 10 minutes. Remove from the heat and cool. Remove the rosemary and cinnamon stick, pour the syrup into a lidded container, and refrigerate for up to 2 weeks.