Adjust oven rack to middle position and heat oven to 325 F. Cook bacon in large nonstick skillet over medium heat until crisp, 6 to 8 minutes. Transfer bacon to medium bowl and pour off fat from pan, reserving 1/4 cup. Cook onion in 1 tablespoon bacon fat until browned, about 5 minutes. Transfer onion and pickles to bowl with bacon.
Pat steak dry with paper towels. Brush 1 side of meat with 2 tablespoons mustard, leaving 1/2-inch border on all sides. Spread bacon mixture over mustard. Starting at long edge, roll steak into tight cylinder and tie at 1-inch intervals with kitchen twine. Season with pepper.
Heat 1 tablespoon reserved fat in now-empty skillet over medium-high heat until just smoking. Brown roast on all sides, about 10 minutes. Transfer roast to 13 by 9-inch baking dish and pour broth into pan. Cover dish tightly with aluminum foil and roast until tender, 1-1/2 to 1-3/4 hours.
Transfer roast to cutting board and reserve pan juices. Heat remaining fat in medium saucepan over medium heat until shimmering. Stir in flour and cook until golden and fragrant, about 2 minutes. Whisk in pan juices and bring to boil. Simmer over medium-low heat until sauce is slightly thickened, about 10 -minutes. Off heat, stir in remaining mustard and pickle juice. Season with pepper. Remove twine from beef. Slice and serve with sauce.