I have never owned a Rottweiler, but it is my understanding that they are oftentimes instructed to guard their home by barking. This would imply that they bark quite a lot.
It’s worth noting, however, that any dog will bark if given enough reason to do so. For example, if someone rings the doorbell or knocks on your front door repeatedly for some time, then your dog will certainly respond with barking. Dogs are pack animals and very territorial in nature–if you happen to live near an industrial park or train tracks where people go walking during the day…