With the Roman Legion about 150,000 strong, there was obviously a a large need for weapons and armor. Before the days of enormous metal casting plants, how would the Romans have gathered all of the (rather complex) equipment necessary for all of the soldiers?
I was interested by your question, and funnily enough my research turned up an old askHistorians thread. You may find it interesting:
Edit: editing to ping /u/HatMaster12 , at the request of the automod. Let the Roman industrial discussions commence.