Despite bad press, this is a calm breed. That said, they are playful animals, usually very excited at the first sign of fun. Rottweilers thrive on attention from their owners and need their people to be happy. If a Rottie has been neglected excessively, he will usually strive, creatively, to get the owner's attention.
The Rottie is not usually a barker: he is a silent watcher who notices everything. In the event the dog feels threatened, he tends to go very still before attacking, and there is no warning growl. This is one of the breed's characteristics that lends itself to the reputation of being unreliable. With an understanding of canine behavior, however, this is not the case. The owner is usually able to recognize when the Rottie perceives a threat. When the dog barks, it is more of a sign of annoyance with external factors (such as cats or other disturbances) rather than threats.
Like many other breeds, the Rottweiler can resort to aggressiveness in unfamiliar situations. For the most part, this is not of grave concern to most dog owners. However, the Rottie's large size and incredible strength make this an important point to consider. For this reason, early socialization with as many strangers (human and otherwise) as possible is very important in order to produce a dog that is friendly to strangers.
Insufficiently socialized Rottweilers may be aggressive with dogs and other animals with whom they are not familiar. For example, Rotties generally behave appropriately towards cats when having been raised with them, but it is not uncommon for poorly socialized Rottweilers to seize and kill cats. Most dogs will, at some point in their lives, attempt to assume the alpha role and lead their owners, rather than vice versa. Being so muscular and powerful, Rottweilers need a firm and experienced owner who can naturally exude leadership. Rottweilers are more likely than most breeds to end up physically stronger than their owners, and this can lead to serious liability issues. Rotties should always be kept on a leash in public