In a large heavy skillet, sauté pork sausage over medium heat until browned and cooked through. Remove from pan and drain; slice thinly and keep warm.
Heat oil in a large saucepan or Dutch oven (large enough to hold about 14 cups/4 L). Add onion, garlic, celery and green pepper; stir and cook until vegetables are softened. Stir in flour.
Add potatoes, carrots, corn and liquid, broth, tomatoes, 1 cup (250 mL) water, bay leaves, and thyme; bring to a boil, and then reduce heat.
Add cooked sausage and cover, simmering until vegetables are tender.
Remove bay leaves and season with salt and pepper to taste. Top off with fresh chopped parsley if desired. Serve with crusty rolls or bread.