Sprinkle roast with salt, pepper, and 2 tablespoons flour. Brown all sides of roast in hot oil in a large Dutch oven.
Combine 1/4 cup water and next 8 ingredients; pour over roast. Add onion. Bring to a boil over medium heat; cover, reduce heat, and simmer 1 1/2 hours.
Add mushrooms; cover and simmer 1 more hour or until roast is tender.
Remove roast, reserving liquid in Dutch oven. Combine 1/4 cup water and 2 tablespoons flour, stirring until smooth. Add flour mixture to liquid in Dutch oven, stirring constantly. Bring to a boil over medium heat; boil, stirring constantly, until gravy thickens. Serve gravy with roast.
NOTE: A pressure cooker will cook this raost in about 40 minutes. Prepare roast as directed, adding all ingredients to cooker. Close lid, and follow manufacturers directions.