I have a uncle who owns two rotweilers that I enjoy seeing. Contrary to belief these can be very good dogs if raised correctly from a young age and not taught to be vicious.
all sources I have on hand say that the rotweiler originated from ancient Rome. In Rome they were used for cattle drovers, pulling carts, and wore their masters purses around their necks on market day. So guard dogs and dog fights were thought of long after the rotweiler was doing these duties.
Resources: The Complete Dog Book 17th edition (AKC)
What You Need To Know To Show Your Dog by :Jeannie Burt (AKC)