Place the carrots, onion, parsnips and garlic into a large bowl. Drizzle with the oil and toss to coat. Spoon the vegetable mixture onto a rimmed baking sheet.
Roast for 25 minutes or until the vegetables are tender, stirring occasionally.
Spoon the vegetable mixture into a 3-quart saucepan. Stir in the broth and heat over medium-high heat to a boil. Stir in the couscous. Reduce the heat to low. Cook for 3 minutes. Stir in the arugula. Cook for 2 minutes or until the couscous is tender and the arugula is wilted.
Divide the vegetable mixture among the pastry shells. Sprinkle with the lemon zest and parsley. Serve immediately.