Reserve 1/2 cup sauteed mushrooms for garnish. Spread remaining mushrooms over cheese. Arrange remaining noodles over. Spread remaining sauce over noodles. Sprinkle remaining Fontina and 1/4 cup Parmesan over. Cover with foil. (Can be prepared 1 day ahead. Refrigerate lasagna and reserved 1/2 cup mushrooms separately. Let lasagna stand 2 hours at room temperature before continuing.) Preheat oven to 350F. Bake covered lasagna 30 minutes. Uncover and continue baking until bubbling and cheese melts, about 20 minutes. Arrange reserved 1 cup mushrooms, tomato and 2 teaspoons rosemary over. Let stand 10 minutes. Cut into squares.