im a bg laddie and i reckon id be toiling to hold 3 rotties if they took it in their mind to take off.
i used to have a big gsd bitch and a boxer x lab that was also huge, bigger than some rotties, used to walk them by myself with no problems, also used to walk the neighbours 2 rotties, they were very strong dogs, wouldnt have been able to handle 3 of them though by any stretch of the imagination. wouldnt try to either.