(condensed from Ein Ayah, Shabbat 1:69)

Gemara: 180 years before the destruction of the [Second] Temple, the Kingdom of Rome spread over Israel.

Ein Ayah: In general, the situation in Israel during the Second Temple was set as a preparation and a gathering of strength in expectation of the long exile that lay ahead. The preparation must be complete to have the necessary great powers so greatly needed for the terribly bitter exile.
If the nation is totally in a tranquil state, even its great people, who need to make the preparations for exile and destruction, cannot possibly absorb the perfect impact of the positive influence. Therefore, the Roman Kingdom spread over them for a long period of 180 years during the time of the Second Temple, when the nation was "armed" with all the physical and spiritual weapons. Anyone with deep perception and feeling already expected that the Israelites’ status in the Land was temporary and would end with destruction and exile. Therefore, while time and sanctity abounded with a functioning Temple serving as a national spiritual center, a plan to preserve the spiritual state was put into action to enable them to survive the long, dark path.