Preheat the oven to 425°F. Line a large baking sheet with parchment paper or lightly grease it.
Trim the carrot tops, leaving about 1 inch of the green tops attached. Peel the carrots and slice each one in half lengthwise. If any carrots are especially thick, cut them into quarters lengthwise so all pieces are similar in size.
In a small bowl, whisk together the melted butter, maple syrup, olive oil, garlic powder, salt, and black pepper.
Arrange the carrots on the prepared baking sheet in a single layer with the cut sides facing down. Brush the maple mixture generously over the carrots, making sure they are well coated.
Roast for 20 minutes. Carefully flip the carrots and brush with any remaining maple mixture. If desired, brush with a little additional maple syrup for a glossy finish.
Continue roasting for 10 to 15 minutes, or until the carrots are fork-tender and the edges are caramelized.
Transfer the carrots to a serving platter and garnish with fresh parsley before serving.