Could you clarify what sort of source you're looking for? I could recommend you some texts from the period, but they tend to be rather inaccessible without context. Jewish theology during this period was incredibly diverse, and part of the issue understanding it is that we often know that others disagreed with the groups we do know about, but not very much beyond that. I also don't know of any comprehensive work that says what Jewish theology during the period was, just ones that discuss smaller issues, though I suspect one does exist.

Some useful sources that do touch on this include:

• Gruen, Erich S. Diaspora: Jews amidst Greeks and Romans. Harvard University Press, 2004. This one discusses a bit of what Judaism looked like in the period, mostly outside Judea.
• Smallwood, E. Mary. The Jews under Roman rule: from Pompey to Diocletian: a study in political relations. Brill, 2001. This one talks about Judaism in the period mostly tangentially.
• Fonrobert, Charlotte Elisheva, and Martin S. Jaffee, eds. The Cambridge companion to the Talmud and rabbinic literature. Cambridge University Press, 2007. This is about Jewish texts more than Jewish religion, and is specific to a particular sect (the one that survived, really).
• Guttmann, Alexander. Rabbinic Judaism in the Making: A Chapter in the History of the Halakhah from Ezra to Judah I. Wayne State University Press, 1970. This is good for this, but is specific to Rabbinic Judaism (or rather its forerunners), and is a little more broad in time than you're looking for, and isn't so much theology.

Some primary sources on religion:

• The Mishnah. Collections of Jewish writings from the 2nd century. Not representative of all sects going backwards, and probably not accessible to the layman.
• Josephus. 1st century Jewish historian. More accessible, but lengthy, and focusing much more on history than religion. Sadly, his planned book about Jewish theology never seems to have been written.
• Philo, 1st century Jewish philosopher. He attempted to synthesize Jewish and Greek philosophy and theology. As a consequence, he's not representative of the less Hellenized crowd, and since didn't even register in importance among Jewish sources I'm usually reluctant to recommend him. He influenced Christianity though (or the ideas which he expressed, but were already circulating among Hellenized Jews did), so things look a lot more similar between early Christianity and Judaism as groups than there was (when that similarity isn't representative of Judaism as a whole).

As you can see, none of these are really superb for your query, unfortunately. Is there a specific question you have?

edited to add a book I forgot about