Roasted Butternut Squash and Spinach Lasagna

“depending on who in my extended family is hosting Thanksgiving dinner, we sometimes have a vegetarian meal. which to me, is not a big deal since the sides are the best part of the meal anyway, and they are mostly vegetarian already. this (without the prosciutto) is one of my go-to vegetarian entrees. crucially, you can assemble it a day or two ahead of time and just bake it off the day of.”