Toss pumpkin cubes, olive oil, and 1 teaspoon salt together in a bowl; spread onto a baking sheet.
Roast pumpkin in preheated oven for 30 minutes, increase heat to 425 degrees F (220 degrees C), and continue roasting until the pumpkin is tender, about 30 minutes more.
Cool pumpkin cubes completely. Trim away outer edges so you have only soft, mashable pumpkin remaining. Measure 2 cups of mashed pumpkin; reserve remainder for another use.
Preheat oven to 350 degrees F (175 degrees C). Prepare a 9x13-inch baking dish with cooking spray.
Mash 2 cups pumpkin, sour cream, and creme de cacao together in a bowl with a potato masher until the mixture is relatively lump-free.
Beat butter and sugar together in a large bowl with an electric mixer until light and fluffy; add eggs one at a time, thoroughly beating each egg into the butter mixture before adding the next. Beat vanilla extract and the pumpkin mixture into the butter mixture with the last egg.
Mix flour, pumpkin pie spice, baking soda, baking powder, and 1/4 teaspoon salt together in a separate bowl; stir into the pumpkin mixture. Fold chocolate chips through the resulting batter and pour into the prepared baking dish.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 50 minutes.