So I'm looking for a final paper topic for my research seminar over Imperial Rome. While Reading Tacitus and Suetonius, there are brief mentions of some Caesars and other prominent figures in Rome keeping freedmen and perhaps slaves in their close circles as colleagues and advisors. My fear in pursuing this topic is the potential lack of good sources as well as information in general. Few are mentioned by name by Tacitus or Suetonius, and these people are not elaborated on much beyond mention. Are there other sources out there that discuss the roles of freedmen among Roman officials?
The research on freedmen and slaves is very extensive. For the former particularly, a wonderful source of evidence is epigraphy, particularly funerary monuments and their inscriptions, but there are also literary sources such as Petronius' Satyricon. However, if you aren't very familiar with the use of epigraphical and archaeological evidence this might be a difficult topic (although not impossible!).
My suggestion would be to start by going to the Oxford Handbooks, which should be in your classical library. In particular, both the Oxford Handbook of Roman Studies and the Oxford handbook of Roman Social Relations have chapters on this. That aside, I have heard good things of the new book The Freedman in the Roman World by Henrik Mouritsen.
Of particular interest to you might be the incident in Tacitus, Annals, XI. 1, 2, 12, 26–38 with Messalina, wife of Claudius. She has an affair and causes a great scandal. In the midst of it all are the freemen Narcissus and Pallas. One of the major criticisms leveled against Claudius was that he let his freeman have too great an influence in the governing of the state.
Barbara Levick's biography of Claudius would be an excellent place to start.