COLUMBIA ELECTRONIC ENCYCLOPEDIA has short biographies of figures in ancient Roman history (via N. S. Gill's Ancient History/Classics blog). Some figures important for ancient Judaism include:

Claudius

Hadrian

Nero

Pompey

Titus

Vespasian

Incidentally, I just ran across De Imperatoribus Romanis: An Online Encyclopedia of Roman Emperors, which is a much more detailed and comprehensive source for Roman emperors. See, for example, the entries for:

Claudius

Hadrian

Julian the Apostate

Nero

Titus

Vespasian

Curiously, neither encyclopedia mentions the Nero Redivivus myth (scroll down to section V) in its "Nero" entry.