2Combine celeriac, carrots, onion, and garlic in a large bowl. Sprinkle with Herbes de Provence, salt, and pepper. Drizzle with olive oil and stir to combine evenly. Spread out vegetables on the prepared baking sheet.
3Roast vegetables in the preheated oven until cooked through, stirring every 19 to 15 minutes, about 40 minutes total.