Prep the carrots. Preheat the oven to 425°F (218°C). If some carrots are thicker, cut them lengthwise in half. In a small bowl, mix together the olive oil and maple syrup.
Roast the carrots. Spread the carrots out on a rimmed baking sheet and drizzle with the oil-maple syrup mixture. Season generously with salt and pepper and toss to coat with your hands. Scatter the thyme sprigs on top. Roast the carrots for 25 to 30 minutes, stirring once after 15 minutes, until the carrots are tender and deeply browned in spots.
Meanwhile, make the gremolata. Finely chop the parsley. Use a microplane to grate the garlic cloves directly over the carrot tops, or just finely mince the garlic with a knife. Then use a microplane to zest the lemons on top of this mixture, taking care to not zest the white pith underneath the skin. Chop everything together until well combined, sprinkle with a bit of coarse sea salt, and then transfer to a bowl.
Once carrots are done roasting, sprinkle the gremolata on top and serve.