Preheat oven to 425°. Place fillets in a 15x10x1-in. baking pan coated with cooking spray. In a small skillet, melt butter; stir in brown sugar, soy sauce, mustard, oil, pepper and salt. Brush half of the mixture over salmon.
Place green beans in a large bowl; drizzle with remaining brown sugar mixture and toss to coat. Arrange green beans around fillets. Roast until fish just begins to flake easily with a fork and green beans are crisp-tender, 14-16 minutes.
