Preheat your oven to 200°C (390°F).
Peel and chop the butternut squash and carrots into uniform pieces so they roast evenly.
Toss the chopped vegetables with olive oil, a pinch of salt, and a splash of maple syrup or honey for a touch of caramelization.
Spread the vegetables on a baking sheet in a single layer and roast for about 40 minutes, stirring halfway through, until they are golden and tender.
While the vegetables roast, chop the onion and garlic. Sauté them in a large pot with a tablespoon of olive oil over medium heat until fragrant and translucent, about 5 minutes.
Add the roasted vegetables to the pot, then pour in the vegetable broth. Bring everything to a gentle simmer and cook for 20 minutes to allow flavors to meld.
Use an immersion blender to blend the soup directly in the pot until it's smooth and velvety. Alternatively, transfer in batches to a blender, blending until silky.
Stir in fresh lemon juice to brighten the flavor, then taste and adjust seasoning with salt and pepper as needed.
Serve the soup hot, garnished with a drizzle of olive oil or fresh herbs if desired. Enjoy this cozy, silky bowl of roasted vegetable goodness!