I think I understand you now.
Throughout history there were a lot of armies that were not subordinated to a state.
They were either loyal to whomever payed them or they where loyal to some religious ideal and tended to break up into little groups.
For a Rothbardian society you don't want a religious affiliated group. Which leaves you the mercenary path.
Now you are left with the question who will decide when it's time for war, and when it's time for negotiations. What to attack etc.
You will need some sort of body to control these mercenaries. A government.
