Arrange a rack in the middle of the oven and heat to 400°F. Place a rimmed baking sheet in the oven while the oven is heating.
Rub the chicken with 1 tbsp olive oil and salt; set aside. In a separate bowl, combine the potatoes, shallots and garlic. Toss with 1 tbsp of olive oil and 2 tsp salt.
Place the chicken skin-side down in the middle of the hot baking sheet. Add the potatoes, shallots, and garlic around the edge of the baking sheet. Immediately return the sheet to the oven, and roast for 15 minutes.
Meanwhile, combine the maple syrup and mustard in a small bowl. In a separate bowl, toss the cauliflower with 2 tsp of olive oil and 1 tsp of salt.
Flip the chicken skin side up. Brush the chicken with the maple-mustard mixture. Then, add the cauliflower to the baking sheet.
Bake until the chicken and potatoes are crispy, about 15 minutes more. Let cool on the baking sheet for 5 minutes before serving.