I know that in Europe in the Middle Ages, craftsmen were often members of guilds, but how did things function during the Roman Empire? Were there guilds? Was there much internal trade in such goods across the empire or were you likely restricted to purchasing such goods as could be made in your own town? Were craftsmen independent businessmen, members of guilds, or employed by local wealthy people? What about the government? Surely the Roman government must have employed many craftsmen to outfit their armies, furnish their buildings, and work on their engineering projects. Were they full-time government employees or more like private contractors? How expensive were crafted household goods (furniture made by skilled carpenters, clothing by skilled tailors etc.)? Would your average Roman citizen own a lot of these things or were they luxuries? How common was it for people to make their own shoes or tools?
Thanks for reading!
Can't speak on the Western half of the Roman Empire but on the Eastern side there were most definitely guilds (collegia) available to merchants or tradesman. Since guilds were spawned from Hellenistic and Roman cities I can assume that they were existent in the Western Empire.
There was plenty of variety among the type of guilds: "There were guilds of butchers, bakers, dyers, ship owners, tanners, perfume sellers, purple-workers, porters, actors.."
In Justinians time (mid 6th cen) these guilds had a specific hierarchy to them and would usually not be bunched together (ex. The Book of Eparch distinguishes the guild of jewllers and silversmiths from the bankers guild even though a smith could easily make a loan). The government did not usually employ guild workers, it is customary that a son takes over his fathers position though it was not made mandatory. Guild membership in the Eastern Empire was free.
A majority of the grain that fed Constantinople came from Northern Africa (at fixed amounts).
TL;DR Let my answer suffice until someone who knows much more comes in.