Preheat oven to 400°F and arrange squash slices on a baking sheet. Drizzle with olive oil, season lightly, then roast until tender and golden brown, about 40–45 minutes.

Sauté aromatics in a large pot over medium heat. Cook onion and carrot for about 5 minutes until soft, then add garlic, stirring until fragrant, about 1–2 minutes.

Combine ingredients by adding roasted squash, vegetable broth, cinnamon, and nutmeg to pot. Bring mixture to a gentle simmer, cover, and cook for 10 minutes to meld flavors.

Blend soup with an immersion blender until silky smooth and velvety, about 1 minute. Adjust consistency with extra broth if desired for a creamier texture.

Season soup with salt and black pepper, tasting as you go to balance sweetness and spice. Warm gently over low heat for 2 more minutes before serving hot.

Garnish & serve by ladling soup into warm bowls. Add a swirl of Greek yogurt, top with fried sage leaves, and sprinkle toasted pumpkin seeds for a nutty, crunchy finish.