A rump roast is made in a slow cooker by adding the roast and seasonings to the slow cooker and cooking it on low for up to 10 hours. When the meat is cooked and tender, vegetables are added for an additional 30 minutes of cooking on high heat.
Remove any netting from the rump roast. Stir together 1/4 cup of chopped onion and one 14.5-ounce can of diced tomatoes in the slow cooker. In a bowl, add 2 slices of chopped bacon, 1 minced clove of garlic and 1 tablespoon of Italian seasoning. Mix well, and rub the mixture over the beef. Place the rump roast into the slow cooker, and cook on low for up to 10 hours or until the meat is tender and fully cooked.
Remove the cooked beef from the slow cooker. In a small bowl, combine 1/4 cup of water with 3 tablespoons of cornstarch. Stir until smooth, and add to the tomato mixture in the slow cooker. Return beef to the slow cooker, and add one 8-ounce package of fresh mushrooms, 1 cup of frozen green beans and 1/2 cup of ripe olives, if desired. Increase temperature of the slow cooker to high, cover and cook for 20 to 30 minutes or until the sauce has thickened and the vegetables are tender.