Preheat oven to 350 degrees. Line a baking sheet with a silicon mat or spray with non-stick spray.
Peel and cube sweet potato into ½" cubes. Place on baking sheet and lightly spray with cooking spray.
Bake until fork tender - about 25-30 minutes. Turning once while cooking.
While the potatoes are roasting, in a large non-stick skillet over medium high heat, wilt the spinach turning it frequently until it gets soft. Work in small batches of spinach. Use immediately or place in a container and refrigerate until needed.