Oven-roasting to a medium-rare level of doneness is the key to preparing tender rolled flank steaks. The flank, located in the underbelly near the animal's back legs, is a muscular area that tends to be tough and fibrous. However, low temperatures and moist heat gradually break down the sinews and connective tissues. Use a meat thermometer because overcooking quickly turns rolled flank steak from tender and juicy to dry and tough.
Place a small amount of olive oil or vegetable oil in a small bowl. Stir in salt and pepper. If desired, add herbs and seasonings like finely chopped thyme, sage and minced garlic. Rub the mixture evenly over all sides of the rolled flank steak.
Coat the bottom of a Dutch oven or heavy, ovenproof skillet with oil. Heat the oil over medium heat, then place the rolled flank steaks in the pan.
Cook the steaks for 8 to 10 minutes, or until the steaks are brown on all sides. Turn the meat frequently with tongs.
Pour beef stock or broth into the pan, and bring it to a boil.
Preheat the oven to 350 degrees Fahrenheit, then transfer the pan to the oven. Insert a continuous-read thermometer into the center of one of the rolled steaks. Roast the rolled flank steaks for 20 or 30 minutes, or until the thermometer registers 145 F. Check the thermometer often to prevent overcooking.
Remove the rolled steaks from the oven and place them on a carving board. Cover the meat loosely with aluminum foil to keep it warm, then let the meat rest for 3 minutes.
Snip and remove the strings, then slice the meat across the grain and serve.