With meat mallet or rolling pin, flatten meat Spread with mustard.
Add bacon, Onion, & Mushrooms over meat.
Roll up meat from short end and secure with string or turkey pins.
Place meat roll in skillet over medium high heat in bacon fat or oil and brown on all sides.
Remove to 13x9 baking dish.
Stir flour into fat in skillet and blend until smooth, gradually stirring in beef broth.
Cook and stir over medium heat until thickened.
Pour sauce over beef roll.
Cover and bake at 325 degrees for 1 1/2 hours or until done.
Let stand 10 minutes before slicing.
Skim fat from sauce, strain and serve with meat.