Preheat oven to 450 degrees F. Oil a rimmed baking pan; set aside. Place sweet potato cubes in a bowl. Toss with the 1 tablespoon olive oil, the chili powder, cinnamon, and sugar. Spread in prepared pan; bake for 20 minutes or until tender.
Meanwhile, cook pasta according to package directions. Drain, reserving 1 cup hot pasta water.
In a saucepan combine peanut butter, cream cheese, chili sauce, and soy sauce; whisk in 3/4 cup of the hot pasta water. Stir over medium heat until heated through. If the mixture is too thick, stir in additional water. Stir in most of the green onions. Serve sauce over pasta with sweet potatoes and remaining green onion slices.