Preheat oven to 475 degrees.
In a large bowl, place Brussels Sprout halves and cauliflower florets. Add olive oil, salt and pepper, and toss to coat; set aside. In a medium bowl, combine cracker crumbs and melted butter; mix to coat; set aside.
Pour onto a foil-lined baking sheet (with sides) and roast for about 15 mintues. After 15 minutes, remove from oven and toss lightly to turn vegetables. Sprinkle buttered cracker crumbs evenly over the top of all the vegetables and return to oven. Continue to roast for an additional 15 minutes or until bread crumbs are golden brown.