Emperors, Court and Travelling Retinue

[Nathan Ross]

Would imperial secretaries normally be slaves/free men/citizens?

As far as I know, they appear to have been mostly freedmen in the earlier 1st century; the Flavians, and particularly Domitian I think, opened up the higher secretarial posts to members of the equestrian order.

I'm sure Millar covers this (it's been a while since I read his book, and I was mainly taking notes on the late empire stuff!). If you can find any biographies of Caligula or Claudius that take a prosopographic approach (as Brian W Jones does, for example, with Domitian), they may suggest the names and origins, wherever known, of principal office holders in the period.

You might also find some interesting material in the first chapter of Millar's Rome, the Greek World and East ('Emperors at Work' - available partly online and as an essay via JSTOR)