Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper for easy cleanup.
Prepare the Vegetables
In a large mixing bowl, toss the carrots and parsnips with olive oil, salt, pepper, and smoked paprika (if using). Spread them in a single layer on the prepared baking sheet.
Roast the Vegetables
Roast the carrots and parsnips in the oven for 20-25 minutes, flipping halfway through, until they are tender and caramelized on the edges.
Make the Kale Walnut Pesto
While the vegetables roast, combine the kale leaves, toasted walnuts, Parmesan cheese, garlic, olive oil, lemon juice, salt, and pepper in a blender or food processor. Blend until smooth, scraping down the sides as needed. Add a little extra olive oil if the pesto is too thick.
Assemble the Dish
Transfer the roasted vegetables to a serving platter and drizzle generously with the kale walnut pesto. Toss lightly to coat or serve the pesto on the side for dipping.
Garnish and Serve
Garnish with extra toasted walnuts and a sprinkle of Parmesan cheese, if desired. Serve warm or at room temperature.