No offense, but the dog that attacked your rottweiler could have been a pitbull!
Had your young child been involved in the middle of a massive fight, this could have turned ugly.
You are both at fault and I would guess that if this goes to court, you will both be in the wrong.
Unfortunately, people with small dogs will usually seem like the victims and you have to consider that a small dog has no defenses against a rottweiler. If I owned a small dog and it was attacked by large dog, I think I would be pretty angry.