Heat the oven to 425 degrees. Coat a large rimmed baking sheet with non-stick cooking spray. Toss the Brussels sprouts with oil; sprinkle with ½ teaspoon salt. Arrange in a single layer on the baking sheet. Bake for 20 to 30 minutes or until the sprouts are crisp-tender. Remove from the oven and toss with the balsamic vinegar. Meanwhile, combine the cottage cheese, sour cream, green onions, dill, tarragon, and black pepper in a blender until smooth. Serve sprouts warm or room temperature with the dip.