Pre-heat the oven to 450-degrees.
Drizzle the beets with ½ tablespoon olive oil and wrap the beets loosely in tin foil. Roast for 40-60 minutes until tender. Cool, peel, and dice the beets into ½ inch cube pieces.
Bring 1 ¾ cups water to a boil in a medium saucepan. Add the couscous and ½ tablespoon olive oil and stir. Reduce heat to low, cover, and cook for 10 minutes until the liquid is absorbed. Turn off heat, stir in arugula to let wilt and let stand for 5 minutes. Set aside.
To make the dressing, whisk together lemon juice, salt, pepper and remaining 3 tablespoons extra virgin olive oil. Add the red onions and let site for 30 minutes. Combine couscous, beets, red onion, scallions, and dressing. Garnish with goat cheese and walnuts and serve at room temperature.