Preheat oven to 375F. put roast in pan with lid and brown both sides using canola oil. Season to taste with black pepper and salt and pour off fat drippings. Into the drippings add ginger,soy sauce,pineapple juice,and onion. Mix well. Return the meat to the pan.
Cover and cook 2-3 hours or until done. When meat is done,remove and keep warm. Skim fat from liquid. Mix cornstarch in water. Add mixture slowly to liquid in pan. Bring to a boil,stirring constantly,and cook until thickened. About 3 minutes.
Taste sauce and correct seasoning,if necessary, with salt and pepper. Slice meat and serve sauce separately.