With Augustus this process reaches more or less its ultimate geographical limits. Now, the main economic driver of the previous five centuries grinds to a halt. Aside from trade with Africa and Asia, all the wealth of Rome is made within its borders. Instead of bringing wealth in to the Empire, the legions just consume it. Rome has no southern neighbor, but they'll squabble with Parthia over Mesopotamia. The Plunder Economy ends and Rome returns to producing for more or less for its consumption. The economic and political situation are relatively stable for the first couple centuries, but in the 3rd and 4th century the wheels start coming off. Those same processes which accumulated enough wealth for a single family to dominate the state eventually produce regional rivals, especially ambitious generals looking to imitate Caesar, and the armies that had a lot to win from backing a successful coup.
So the constant warfare blood Rome dry financially as generals vie for the crown, then successive plagues depopulate it, just when migrations from Asia displace peoples bordering Rome. Some who come and settle peacefully, and who the Romans are only too happy to accept so that there's someone to do all the work that needs doing, but also the fighting that needs fighting. All this fighting naturally wrecks the economies of entire provinces, not only damaging production, but literally killing their markets as well. A negative feedback loop occurs, where increasingly damaged economies spur army recruitment, who go to war to kill other Romans, damaging the economies further, which only increases the incentives to revolt, which damages the economy further as the state pays out tremendous indemnities…
All these and other factors put so much pressure on Rome that it begins to collapse. With international trade either dead or impossible (because of plague or rebellion etc) these regions more or less begin to or have to start fending for themselves. The Empire persists until the 450s or so more or less by inertia. Imbuing so much legal authority into a single individual comes back to bite as the sheer size and scope of the Empire overwhelm the ability of an individual to manage it. The centralization of state power eventually comes to mean that "Rome" is wherever the Emperor was, and anywhere else was up for grabs.
The Germans invade and divvy up Rome. The crumbling Roman economy completely falls apart and international trade more or less comes to a standstill. A semblance of it will continue in the Eastern Roman/Byzantine empire until the Muslims come along. Part of what eases Islam's expansion through ancient mainstays of the Roman empire was the economic order they brought with them as opposed to former Roman bureaucrats or constantly warring Germans.
But what we're ultimately left with at the end of Antiquity and the beginning of the Middle Ages, everything that made economic sense for the past millennium went up in sometimes quite literal smoke. The only places that weren't on fire belonged to the Church or landowners materially sufficient in supplying the needs of a small army. If you were a cobbler, or smith, or sheep herd, or whatever, you could either try and tough it out in cities overrun with slave labor or make yourself and all of your descendants slaves to a local Count or Jarl or whatever they want to call themselves into perpetuity. Trying anything else resulted in a violation of the NAP and the Duc's private army fucking murdering you. :^)
While distinct, the ancient and modern economy both result in similar patterns of material accumulation, concentrating wealth into hereditary, and in the case of corporations perpetual, ownership. I'd like to think that we we won't see outright slavery, but I wouldn't doubt its Capitalism With A Human Face, corporate equivalent. "How nice of google to build a whole town for its employees. Ha! 'Googlebux,' can you imagine?"