[candiodari]

As the MASSIVE aquaducts in France and Italy clearly illustrate, as well as things like the Thermae, the Romans were keenly aware that there are things that can't be done with any amount of slave labour, and did in fact use labor saving devices.

Hell, they had the same problem we have: "automation" (massive infrastructure projects) putting people out of jobs. The solution was also similar: first, massive infrastructure projects soaking up more than all available labor for decades, followed by making the problem worse, then austerity and mass-corruption on all levels, then (let's say "todo" in our current case) revolution, followed by large scale Rome-initiated expansion wars. On the plus side: those wars resulted in the longest period of prosperity in history.