Preheat oven to 350°F. Rub roast all over with pepper; season with salt.
Warm oil in a large ovenproof skillet over medium-high heat. Place roast in pan and cook, turning every 2 to 3 minutes, until browned on all sides, about 10 minutes total. Remove pan from heat, pour molasses over roast and turn roast to coat in molasses.
Place skillet in oven and cook until center of roast registers 140°F on an instantread thermometer, 40 to 50 minutes, basting with pan juices once or twice during roasting. Transfer roast to a cutting board (preferably one with a lip to capture any juices), tent with foil and let rest for 15 minutes. Set aside pan with juices.
Remove twine and slice roast. Add accumulated juices on cutting board to pan juices and serve with roast.