I've been associated with Rottweilers since 1988.
This is another breed that in many countries, including the country of origin, where they are bred, if they can not face a human adversary with complete courage, and bite to defend themselves or their handler, they are not used for breeding.
Both my adult bitches are well versed in the bad guy and what to do if the need arises.
They are both also quite sociable, friendly, touchable and approachable by any person in a normal situation.
Should anyone threaten me, or invade my property when I am not present, they most CERTAINLY would defend me and bite if necessary, and I would expect them to. It's MY JOB to protect the dog from doing what it is genetically designed to do. It's MY JOB to socialize and train and confine that dog so that he understands what is and is not a threat, and so that he is always under my control, for his/her own safety.
You would never feel uncomfortable around my dogs in my home, or on the street, or at any dog show. They are just like any other dog, except if a threat arises, they have been well trained in what to do, and more importantly, what NOT to do.
Any fool can teach a dog to bite. It's teaching them when NOT to bite where the training comes in.