Robin Roberts and the anchors of “Good Morning America” had a dance-off at their spring cocktail bash — which Lara Spencer won by grooving to Jay-Z. The “GMA” gang was at Hudson Terrace Wednesday when a dance battle broke out between Roberts, Spencer and Josh Elliott. “Lara won when a producer jumped onto a go-go platform and pulled her up to dance to ‘Empire State of Mind,’ ” a spy said. George Stephanopoulos stayed out of the fray and enjoyed the show while sipping a drink.