Add 4 cups of water (or enough to cover the lentils plus about 2 extra inches) and the lentils to a medium-sized, deep saute pan over medium heat. Cook with the lid just slightly off the pan, for about 15-20 minutes or until the lentils are almost tender.
Meanwhile, if you're using bacon (or pancetta), add it to a saute pan and cook over medium-high heat until done. When cooled, crumble the bacon into small pieces and set aside.
In a large, deep saute pan over low-to-medium heat, add the olive oil. When hot, add the onion, carrots, garlic and celery and cook until almost soft. Add the tomato sauce, parsley, cream of mushroom or celery soup, 3 cups of water, and salt & pepper to taste. Bring to a boil. Once boiling, add the pasta, lower the heat and cook until the pasta is tender.
Drain your lentils when they're almost soft and add them to the pasta and cook, uncovered, for another 10-15 minutes until they're soft. Add the red pepper flakes and adjust the seasonings to your taste. If you think your soup should be a bit creamier, make a roux (I used 1 tablespoon butter and 1 tablespoon flour and that was sufficient) and slowly whisk it into the lentil and pasta mixture and make sure it's incorporated into the soup. If you like it thinner, add a bit more water. Add your bacon or pancetta if your using it and mix it into the soup.
When you're ready to serve, add to individual bowls and sprinkle with fresh grated Romano cheese.