For this particular lasagna dish, you will want a deep baking dish.
Brown both sausage and ground beef. Drain well, mix completely, and set aside.
Thaw spinach and hand-squeeze as much water from spinach as possible. Mix spinach, ricotta cheese and egg to a nice smooth consistency. Add garlic salt, onion salt, pepper and any other spices you may like. Leave cheese at room temparature as this makes it easier to layer into lasagna.
Mix spaghetti sauce and alfredo sauce together. Pour an even layer of sauce into bottom of baking dish. Place a layer of lasagna noodles onto sauce.
Now you can layer your ingredients any way your taste leads you. In my experience, the ricotta cheese does better on the bottom layers. You may make as many or as few layers as you want. Also, don't be too conservative with your sauce, since the pasta you will be using is dry and will absorb some moisture while baking.
Once you've completed construction of your edible masterpiece, cover it with aluminum foil and place into a pre-heated 350°F oven for 45 minutes.
Remove lasagna from oven and remove aluminum foil. Place back in oven for about 10 minutes to allow the top to brown slightly. Allow to cool 15-20 minutes to set layers before serving.