Trainer's POV: As some suggested -- overall basic training is essential. Problem solving, especially agression, is tough w/o a structure for the dog to connect to. Second, read "How to be your Dog's Best Friend" by the Monks. Pages 40 to 54. Forget the "rollover." The "under the chin" works best. Seems harsh, but you must be tough in this situation. Besides, once your dog understands you are the boss and have "relieved" it of the burden of feeling he has to protect you, he will be much more relaxed and happy. Don't worry -- when push really comes to shove he will protect you.