Add roasted cauliflower, mushrooms, garlic, salt, broth and eggs into a bowl and blend with a stick blender or place in regular blender and pulse until mixture resembles ricotta. Set aside.
For marinara sauce, combine all sauce ingredients in a bowl or saucepan and mix well.
Lightly grease a 9x13 pan with olive oil. Have your bowls of sauce, cauliflower ricotta and sausage handy along with the noodles. Layer as follows: 2 cups sauce, 4 noodles, ½ of the ricotta mixture, ½ of the sausage, 2 cups sauce, 4 noodles, last ½ of the ricotta mixture, last ½ of the sausage, 2 cups sauce, 4 noodles, remaining sauce (approx. 2 cups).
Slice three bell peppers and layer on top.
Cover with aluminum foil and bake 60 minutes at 350 degrees. Remove foil and turn on broiler for 10 additional minutes. Remove from oven and let rest 15 minutes before serving.
Notes
If you prefer to steam the cauliflower, this works too, just omit the broth in the cauliflower ricotta layer.
Also delicious if you add ½ cup parmesan or manchego to the cauliflower ricotta mixture. Can be topped with mozzarella as well for any who wish to add a little cheese.
You can freeze this by letting it cool completely after baking. Cover with a layer of plastic wrap, then 2 layers of aluminum foil. Freeze up to 2 months. To reheat, let thaw until center is no longer frozen but still cool and bake at 350 degrees about 45 min to 1 hour until hot throughout.