Heat oil in heavy large pot over medium heat. Add onion; saute until translucent, about 4 minutes.
Add garlic; cook 1 minute.
Add sausage; cook until browned, breaking up with back of spoon, about 5 minutes. Drain drippings from pot.
Add diced tomatoes with juice, crushed tomatoes, basil and oregano; increase heat and bring to boil. Reduce heat to low and simmer 30 minutes to blend flavors, stirring occasionally.
Meanwhile, cook pasta in large pot of boiling salted water until tender but still firm to bite, stirring occasionally. Drain.
Stir pasta and spinach into tomato sauce. Simmer until spinach wilts, stirring often, about 2 minutes. Season with salt and pepper.
Transfer to large bowl. Sprinkle with Parmesan.