Italy, Greece, Anatolia, the Levant, North Africa, parts of Spain, Crimea, and Armenia and mesopotamia for the brief period they controlled them. ie, the areas containing the vast majority of the population and economic productivity of the empire.

Now, few of these regions had an overarching government or civil service - but they were all developed regions made up of various kingdoms, empires and city states, and each of those had their own elites and methods of economic management and tax collection.

Egypt was pretty unique in its size, wealth, history and organisation, but in the vast majority of places they conquered the Romans worked with existing power structures and elites (where they didn't wipe them out).

As the piece notes, Gaul and Spain were in the very early stages of that process, but the rest of the empire - the areas to the south, southeast, east, and northeast of the Mediterranean - all did. Greece was a comparative newcomer.

You can fruitfully think of administration as a phenomenon which originates in Egypt and Iraq and radiates outward from there.