If the carrots are thick, cut them in half lengthwise; if not, leave whole. Slice the carrots diagonally in 1½-inch-thick slices. (The carrots will shrink while cooking, so make the slices big).
Place the carrots in a large bowl and toss with olive oil, salt and pepper.
Transfer to a sheet pan in 1 layer and roast in the oven for 20 minutes, until lightly browned and tender. Toss the carrots with minced dill or parsley, season to taste and serve.