Start by preheating the oven to 425 degrees F. Slice the top of 2 full heads of garlic and place in a piece of aluminum foil. Drizzle olive oil on top and sprinkle with salt and pepper. Close the aluminum foil around it and place on the oven rack for about 40 minutes, until garlic is mushy. Reduce heat to 350 degrees F.
While the garlic is roasting, saute sausage and red onions together in a skillet. Then add the mushrooms and cook until mushrooms and onions are completely cooked down and soft. Add in the seasonings, stir together and set aside.
After the garlic is finished roasting, squeeze out the garlic cloves onto the aluminum foil and set aside. Melt butter in a skillet and then add flour. Stir together to make a paste then add milk, salt and pepper, rosemary, thyme, nutmeg, and the roasted garlic. Whisk constantly until the sauce thickens. Remove from the heat and in parmesan cheese.
In a 9x13 baking dish, thinly coat the bottom of the dish with the roasted garlic sauce. Place 3-4 lasagna noodles on top. Then add the sautéed sausage/onion/mushroom mixture, top that with kale and mozzarella and asiago cheese. Repeat this. Then cover with aluminum foil and bake for 35 minutes. Uncover and continue to bake for another 20 minutes, until cheese is slightly browned.