Roast beef uncovered 40 minutes, brushing beef occasionally with reserved marmalade mixture. Meanwhile, in another small bowl or cup, mix thyme, salt and pepper. Sprinkle top and sides of beef with 2 teaspoons of the thyme mixture. Place potatoes around beef. Generously brush potatoes with some of the 3 tablespoon marmalade mixture; sprinkle with half of the remaining thyme mixture.