Heat the oven to 425°F and let it preheat for 10 minutes. Meanwhile scrub 12 medium carrots and peel only rough patches. Trim the tops and halve each carrot lengthwise with one firm cut. Keep every piece 5 to 7 inches long. Aim for shoulders between 1/2 and 1 inch thick so all 24 halves soften together. Spread the 24 carrot halves out and compare their thickness. The cut faces should look moist and bright orange while the pointed ends stay intact. Uneven shapes are natural but no piece should be dramatically thicker. Miss this size window and thin tips scorch before thick centers soften. Even halves expose enough surface for steady caramelization.

Keep the melted butter near 100°F so it stays fluid. Whisk pure maple syrup with light brown sugar, butter, extra-virgin olive oil, cinnamon, kosher salt, black pepper and chopped rosemary for 60 to 90 seconds. Use fast circles until no sugar lumps remain. Add all 24 carrot halves and fold from bottom to top for 2 minutes. The glaze should cling in a thin amber film and gather lightly along each cut face. You'll smell cinnamon and maple before the carrots reach the pan. Dry patches mean the bowl wasn't scraped. (I once left them coated for 20 minutes, the bowl filled with orange liquid.) Wait too long and salt pulls out water. A thin coat roasts instead of steaming.

Transfer the 24 glazed carrot halves to an 18×13-inch rimmed sheet pan. Arrange them cut-side down in one loose layer with small gaps. Roast at 425°F for 15 minutes without stirring. Press each flat face against the metal before the pan goes in. That direct contact starts the dark caramelized stripe seen on finished carrots. At minute 15 the glaze should bubble quietly around the edges. Lift one carrot and look for a bronze cut face with darker spots near the shoulder. The rounded sides will still look bright orange and slightly firm. Crowd the pan and trapped steam makes the glaze pale and watery. Direct metal contact concentrates the sugars before the centers soften.

Flip every carrot so the bronze cut face points upward. Shift the pieces toward open areas and brush the pooled pan glaze across their tops. Return the same sheet pan to the 425°F oven for 12 to 15 minutes. Rotate the pan once at minute 7. Remove it when a fork meets only slight resistance at the thickest shoulder. The carrots should turn deep mahogany-orange with glossy ridges and darker caramelized edges. Their tips will wrinkle slightly and the maple aroma will smell toasted rather than raw. Go past 15 minutes and the sugar can taste bitter. At 18 minutes the darker glaze starts masking the clean maple flavor. The second roast sets a lacquer without drying the centers.

Rest the carrots on the sheet pan for exactly 3 minutes off the heat. Then transfer 6 halves per serving to a plate while they're about 150 to 160°F. Spoon a little thick pan glaze over the top. Scatter pomegranate arils, reserved rosemary needles and flaky sea salt unevenly so the orange surface still shows. The glaze should stop bubbling and turn tacky enough to hold each garnish. Ruby arils will sit between the carrot halves instead of sliding into a puddle. Plate immediately and the glaze runs thin. Wait longer than 10 minutes and the surface loses some shine. A short rest lets dissolved sugars thicken around each carrot.