Preheat oven to 350 degree F. Remove casings, if present, from sausage. In a skillet cook and crumble sausage; drain. In a very large bowl combine sausage, cooked pasta, cream cheese, bread cubes, olives, and mozzarella cheese. Set aside.
In a medium saucepan melt butter over medium heat. Stir in flour, sage, thyme, salt, and cayenne pepper. Add milk all at once. Cook and stir until slightly thickened and bubbly. Pour sauce over pasta mixture. Stir gently.
Transfer mixture to a 2-quart casserole. Bake, covered, for 35 minutes. Uncover; top with tomato slices and Asiago cheese. Bake, uncovered, 15 minutes more or until heated through. Let stand 15 minutes before serving. Sprinkle with additional fresh thyme, if desired.