Wash and chop the vegetables: dice the onion and bell pepper, mince the garlic, and cut carrots, celery, russet potato, and sweet potato into small, uniform pieces. Slice zucchini and yellow squash into half-moons.

In a large pot, heat the olive oil over medium heat. Add diced onion and sauté for about 5-7 minutes until translucent. Stir in minced garlic and cook for an additional minute.

Introduce russet potato, sweet potato, and red bell pepper. Pour in vegetable broth and diced tomatoes. Season with thyme, rosemary, red pepper flakes, salt, and pepper. Bring to a boil, then simmer for 20-25 minutes until potatoes are tender.

Stir in chopped zucchini and yellow squash and cook for an additional 5-7 minutes until soft.

If desired, purée the soup for a smoother consistency. Stir in heavy cream or coconut milk, heating gently over low heat.

Taste and adjust seasoning as necessary.

Ladle soup into bowls, garnish with parsley, and serve with crusty bread.