1. Whisk together first 5 ingredients in a lightly greased 5-qt. slow cooker. Stir in mushrooms. Add roast to slow cooker. Cover and cook on HIGH 4 to 4 1/2 hours or until beef is tender and shreddable.
2. Meanwhile, prepare noodles according to package directions. Toss hot cooked noodles with 2 tablespoons parsley.
3. Spoon beef mixture over hot cooked noodles. Sprinkle with remaining 1 tablespoon parsley, and serve immediately.