Bring sauce to room temp or reheat gently on stove. Cook 2 pounds spaghetti in boiling, salted water until al dente, 8 or 9 minutes. Drain.
In a large baking pan, put a little sauce to coat the bottom entirely. Add a layer of pasta, ladle some sauce all over the top, sprinkle on half the shredded cheddar. Repeat with another layer of spaghetti, more sauce, the rest of the cheddar.
Cover cheddar with remaining spaghetti. Ladle some more sauce over the top and then sprinkle with grated Romano cheese. So here's what you have, sauce, spaghetti, sauce, cheese, spaghetti, sauce, cheese, spaghetti, sauce, Romano.
Cover with foil and bake in 350º oven for 45 minutes. Remove foil and bake another 15 minutes, until heated thoroughly and cheese is melted.
Serve, passing more Romano and extra sauce if desired.