In a 9 x 13-inch casserole dish, add a little marinara sauce to the bottom, just enough to coat the bottom and prevent the pasta from sticking. Layer the sauce with cooked lasagna noodles, more sauce, chicken, more lasagna noodles, more sauce, pumpkin pieces (you don't have to completely cover the noodles and sauce), and repeat...lasagna noodles, sauce, chicken, noodles, sauce, pumpkin, and finally, sauce.
*To Roast Sweet Potatoes:
Preheat oven to 425ºF. Peel the sweet potatoes, slice in the shapes you desire, about 1/2-inch thickness. Add to a baking sheet. Coast with oil and roast until tender, turning over halfway through, a total of about 25 minutes. Do not over-bake or they will be mushy. You want them to keep their shape.
Use creamy gluten free pesto sauce mixed with a little pasta water to thin it out instead of marinara sauce. I like this Creamy Dairy-Free Cheesy-Tasting Pesto Sauce.
Mashed Pumpkin or Sweet Potatoes:
If you over-bake the pumpkin or sweet potatoes, just mash them up. When it's time to layer the lasagna, just spread a thin layer over the noodles and then add the sauce over the pumpkin.