In a small saucepan, combine RTC juice, sugar, and rosemary sprigs.
Bring to a boil, and then reduce the heat to a simmer, stirring occasionally. Allow to simmer for 10-15 minutes, or until the syrup has thickened slightly and has been infused with the rosemary sprigs.
Discard rosemary sprigs. Spike with your favorite spirit, if desired.
Make the Punch:
This can be made in large batches, or assembled in individual glasses. Add equal parts cranberry juice and ginger beer.
Stir in syrup until desired sweetness is achieved (we recommend 2-3 tablespoons per glass).
Serve with ice and garnish with fresh rosemary, tart cherries, or sugared cranberries.