The prophet Obadiah was a convert from the nation of Edom, who were descendants of Esau and the spiritual (if not literal) forebears of the Roman empire. Obadiah prophesized regarding their ultimate fate. The Radak explains this verse as follows: the Romans raised their glasses and rejoiced over the destruction of the Temple. Ultimately, they would be destroyed to such an extent that the places they inhabit would be completely unrecognizable. It would be as if they had never even existed.