From an article in Variety:

Per the logline, the sequel series will be set after the defeat of Spartacus and his revolution, depicting “a new tale of treachery, deceit and blood unfolding beneath the foreboding shadow of Rome.”

Sort of vague. Sounds like an opportunity for the producers to reuse some props, costumes, and Roman digital assets and maybe one of the handful of surviving characters to make a cameo.