Preheat oven to 425°F. Line a rimmed baking sheet with parchment.
Open pastry sheet and lay flat on a lightly floured surface. Place Brie in center of dough. Spread jam on top of Brie, and then sprinkle with cranberries, rosemary and pecans. Fold dough up and over to enclose cheese and filling, pleating dough to fit. Trim any excess pastry and press seams to seal. Transfer to baking sheet. Whisk egg with 1 tsp. water and brush outside of pastry with egg wash. Press a few pecan halves into top of dough to decorate, if desired.
Bake until dough is golden, about 20 minutes. Let cool slightly. Serve with crackers, fresh figs and grapes, if desired.