Preheat the oven to 400°F
In a large mixing bowl, toss the sweet potato with 1 tablespoon of olive oil, 1/2 teaspoon nutmeg, and 1/4 teaspoon salt.
Spread the sweet potato on a lined baking sheet and roast for 15 minutes.
Toss the celery and onion in the remaining tablespoon of olive oil, 1/2 teaspoon of nutmeg, and 1/4 teaspoon of salt.
Stir in the celery and onion with the sweet potato and continue roasting for another 20-25 minutes until the vegetables are tender.
Meanwhile, bring a dry skillet to medium heat and add the walnuts. Toast, stirring often, for about 5 minutes until fragrant and golden brown.
Whisk together the vinaigrette ingredients in a mixing bowl. Add the roasted vegetables and arugula and toss to coat.
Top the salad with the toasted walnuts and pomegranate seeds.