Preheat your oven to 220°C (430°F). Line a baking sheet with parchment paper to prevent sticking and for easy cleanup.
Wash and peel the carrots if desired, then cut them into uniform 2-inch pieces. Snap off the woody ends of the asparagus and halve thicker spears for even roasting.
In a large mixing bowl, toss the carrots and asparagus with 3 tablespoons of olive oil, ensuring each piece is lightly coated. Add salt, pepper, minced garlic, and herbs if using, then toss again to distribute evenly.
Spread the vegetables in a single layer on the prepared baking sheet, making sure they aren’t overcrowded so they can caramelize properly.
Roast in the oven for about 20-25 minutes. After the first 10 minutes, gently shake the tray or use tongs to flip the vegetables for even browning and caramelization.
Check for doneness: carrots should be golden and tender, and asparagus tips slightly charred and smoky. If needed, roast for an additional 3-5 minutes until they reach your preferred level of caramelization.
Remove from the oven and immediately squeeze fresh lemon juice over the vegetables for brightness. Toss gently to combine and enhance their flavors.
Transfer to a serving platter or serve directly from the baking sheet. Garnish with extra herbs if desired, and enjoy the warm, tender, and caramelized bites of this simple dish.