I know that legionaries were responsible for providing their own armor and standardized equipment was not a thing until the empire (I think) but what would the armor making scene have been like in ancient Rome as compared to the Medieval period?
In many cases the state produced them. Soldiers would pay the quartermaster for their weapons and armor. I seen many cases because there were time periods when the professionalism of the army was very low and soldiers were allowed to buy their own equipment.
The theory was the state would produce all of the arms armor and uniform of a soldier's kit. A soldier would receive one free everything upon becoming a soldier and if something had to be replaced they would take it out of their salary to buy it from the state. If you kept your equipment in good order you wouldn't have to buy new equipment as often and you could keep the money, otherwise a percentage of your salary was in theory supposed to go towards your equipment.
edit I'm talking about the high point of the Empire by the way. During the Roman Republic citizens would provide their own equipment. And during the late Republic generals would furnish their soldiers with their own equipment at first and a soldier would have to buy replacement equipment.