Chop up the tomatoes, bell pepper, onion, and garlic cloves. Put them on a baking sheet with olive oil, salt, and pepper. Bake in the oven at 425F for 30 minutes to roast.

Add the roasted vegetables into the slow cooker and add the seasonings. Pour the vegetable stock and cover with the lid to cook on HIGH for 2 hours.

Use an immersion blender or regular blender to blend everything until a smooth consistency.