Stir squash, garlic, 1 tablespoon oil, 1/4 teaspoon salt and 1/4 teaspoon pepper together in a large bowl. Spread on a large rimmed baking sheet and roast, stirring once, until tender, about 20 minutes.
Meanwhile, whisk the remaining 2 tablespoons oil, vinegar, maple syrup, mustard and the remaining 1/4 teaspoon each salt and pepper in the large bowl. Add spinach, the roasted squash, apples, cheese and pecans. Toss to coat.