Heat the sesame oil in a heavy oven-proof or cast-iron skillet over medium-high heat until the oil shimmers, and sear all sides of the roast, including the ends, to a golden brown color. Lay the roast into the skillet, place into the preheated oven, and roast to your desired degree of doneness, or an internal temperature of 145 degrees F (65 degrees C) for medium, about 40 minutes. Remove from the oven, cover with a doubled sheet of aluminum foil, and allow to rest in a warm area 10 to 15 minutes before slicing.