Preheat oven to 425F.
Trim off the tops of the carrots leaving a few inches of green. Scrub carrots clean with a vegetable brush under running water.
If the carrots are large, cut them in half.
Mix the marmalade, brown sugar, the zest of both oranges, the juice of one orange, and the butter or oil.
Place carrots in your roasting pan; I use cast iron; if you are not using cast iron, I suggest laying down a sheet of parchment paper for easier cleanup.
Pour the marmalade mixture over the carrots and toss well.
Cover with foil, and place in the oven for 20 minutes
Remove the foil, and using tongs, stir the carrots and roast for 15 to 20 more minutes, uncovered until the desired doneness.
Remove the carrots to a serving dish, pour the remaining sauce over the carrots, and using tongs, squeeze the hot oranges over the carrots.