1. Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius).
2. Grease a nine x 13-inch (20×30-centimeter) baking pan with butter.
3. Pour half the marinara sauce on the bottom of the pan. Add half the béchamel sauce in dollops on top. Lay filled cannelloni one near the other in the sauce (you may need another small pan). Repeat layers of sauce, covering all the tubes.
4. Cover well and bake for 40 minutes.
5. Remove from oven and sprinkle with shredded cheese.
6. Cover and return to the oven for another five minutes.
7. Uncover and bake for five more minutes. Let sit for a few minutes, covered, before serving.