In the bowl of a stand mixer with the paddle attachment on, beat butter and dark brown sugar for 3 minutes, or until lightened in color. Add eggs one at a time; stir to combine. Add molasses and vanilla extract, and stir until combined. Add applesauce and combine. Add flour/spices mixture slowly to mixer, on low, scraping down sides with spatula until evenly combined. Add rolled oats, stir until combined.