Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a large bowl, toss the chopped vegetables with olive oil, salt, and black pepper until evenly coated.
Spread the vegetables in a single layer on the prepared baking sheet. Roast in the oven for 25-30 minutes, or until they are tender and slightly caramelized.
Once roasted, transfer the vegetables to a large pot. Add the vegetable broth, garlic powder, and dried thyme. Bring to a simmer over medium heat.
Use an immersion blender to puree the soup until smooth. If you don’t have an immersion blender, carefully transfer the soup in batches to a countertop blender and blend until smooth.
Stir in the heavy cream and lemon juice. Heat the soup for an additional 5 minutes, allowing the flavors to meld. Adjust seasoning if necessary.
Serve hot, garnished with fresh parsley.