Add the pomegranate seeds, pomegranate juice and water to a silicone Bundt pan. Freeze until solid, 3 to 4 hours or overnight. When ready to serve, run the ring mold under a little hot water, remove from the pan and place in a large punch bowl.
For the pomegranate lime punch:
Add the pomegranate juice, vodka, orange-flavored liqueur and lime juice to a large punch bowl and stir to combine. Add the ring mold and top with the Champagne just before serving. Garnish with the rose petals.
Using a silicone Bundt pan to make the ring mold helps the frozen ice mold pop out easily.