Preheat oven to 425 degrees. In a large saucepan, cover potatoes with water; bring to a boil, and add 1 teaspoon salt. Cook until potatoes are slightly soft on the outside, about 12 minutes. Drain; return to pan. Add 1/2 teaspoon salt and 1/2 teaspoon pepper. Shake pan to soften edges.
Pour oil in a large roasting pan; place in oven. On a plate, mix together flour, dry mustard, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Dredge beef in flour mixture, turning to coat all sides.
Transfer potatoes to hot roasting pan; toss to coat. Place beef in center of pan; roll in oil, leaving fat side up. Roast until beef is 120 degrees. 40 to 45 minutes. Turn potatoes after 15 minutes of cooking.
Remove potatoes and beef. Cover; let beef rest about 20 minutes before slicing thinly to allow temperature to reach 135 degrees.to 140 degrees.for medium-rare.
Place roasting pan over medium heat. Add broth; simmer, scraping bottom of pan, about 1 1/2 minutes. Serve sauce with beef and potatoes.