Heat oil in a large pot over medium heat.

Trim fat from roast and cut into 1-inch cubes. Place meat into hot oil in the pot. Add onion and garlic; cook and stir until meat is browned and onion is tender, 5 to 7 minutes.

Pour in water, broth, and tomatoes. Stir in mixed vegetables, celery, and mushrooms. Season with oregano, thyme, basil, parsley, and cayenne; bring to a boil. Reduce heat, cover, and simmer for 1 hour 15 minutes.

Stir pasta into soup; cook until tender, about 10 minutes.