Increase oven temp to 400 degrees.
Mix cranberry sauce ingredients together in a medium bowl and trasfer to a 9x13 baking dish.
Bake until the berries burst, about 20 minutes.
Allow to cool completely, and chill until ready to serve.
Slice brie into 48 slices and place on the crostini. Evenly divide cranberry sauce among brie topped crostini.
Top with a little extra orange zest and rosemary and serve!