Lightly coat large baking sheet with cooking spray.
In a small bowl whisk together oil, vinegar, orange zest, orange juice, salt and pepper.
Arrange carrot, beets, leek, sweet potato and onion in single layer on baking sheet. Sprinkle with tarragon. Drizzle oil and vinegar mixture over vegetables. Bake 30 to 35 minutes, stirring occasionally.
When vegetables are tender, remove from oven and serve immediately.
Leftovers may be covered and refrigerated. Vegetables may be served hot or cold.