Preheat oven to 425°. Cut carrots crosswise on a bias into 2" to 3" pieces. Cut thicker pieces in half lengthwise.
On a large baking sheet, toss carrots with garlic, oil, ½ cup Parmesan, ½ teaspoon salt, and a few grinds of pepper. Spread in a single layer.
Bake carrots until tender and caramelized in spots, 25 to 30 minutes.
Transfer carrots to a platter. Toss with lemon juice. Sprinkle with parsley and remaining ¼ cup Parmesan and toss just to combine.
