A dog wagging its tail and roaring at you may want to get close to you, want to play with you, or is warning you, etc. It is usually caused by being too excited and is a normal phenomenon. If it is a familiar dog Don’t worry too much; if it’s a strange dog, it’s best to stay away to prevent the dog from attacking people.
Tip:
Most people think that a dog wagging its tail means it is friendly, but some dogs also bite when they wag their tail. Human condition, so be careful.