Position rack in center of oven, and preheat oven to 425°. Pat fish dry; make several diagonal cuts in thickest part of the fish on both sides. Scatter sliced fennel bulbs, leeks, and tomatoes in a baking pan lightly coated with cooking spray.
In a small bowl, whisk together olive oil, garlic, salt, and pepper. Brush fish inside and out with half the seasoned oil, then sprinkle remaining seasoned oil over vegetables. Lay fish on top of vegetables, and sprinkle fish inside and out with fennel seeds. Tuck 1 rosemary sprig into cavity of fish. Place remaining 2 rosemary sprigs in vegetables. Reserve a couple of fennel fronds for garnish, then coarsely chop remaining fronds and stuff them into the cavity. Pour wine over fish, and cover pan loosely with aluminum foil.
Bake at 425° for 30 minutes. Remove foil, and bake, uncovered, 10 to 15 minutes or until fish is just cooked through. Transfer fish to a large serving platter, and surround with cooked vegetables. Garnish with remaining fennel fronds.