Trim and peel or scrub carrots, leaving about 1 1/2-inch of carrot tops, if present. Halve any thick carrots lengthwise. Place in a 4-quart Dutch oven along with the rosemary sprigs. Add lightly salted water to cover. Bring to boiling; reduce heat. Simmer, covered, for 8 to 10 minutes or until crisp-tender.
Drain in a colander; remove and discard rosemary sprigs (some rosemary leaves will remain). Add butter to Dutch oven; heat just until butter is melted. Return carrots to Dutch oven and toss to coat. Arrange carrots on serving platter. Top with some of the jelly. Pass remaining jelly.
Test Kitchen Tip: To substitute for wild grape port jelly, in a small bowl whisk together 1/4 cup grape jelly and 1 tablespoon port, grape juice, or apple juice.