How to Make It
Preheat the oven to 350°. Put the beets and carrots in two separate baking dishes and lightly drizzle both with olive oil. Cover with foil and bake until tender, about 45 minutes for the carrots and 1 hour for the beets. When cool enough to handle, peel the beets and cut into twenty-four 1 1/2-inch-by-1/2-inch sticks.
Light a grill. Alternately thread 2 each of the beet, carrot and scallion pieces onto 12 bamboo skewers. Drizzle lightly with olive oil and grill until lightly browned, about 2 minutes per side. Transfer the skewers to a platter and drizzle with a little more olive oil. Season with salt and pepper, sprinkle with the tarragon and serve.