Magnus Cort put in a hectic sprint to give EF Pro Cycling a third stage victory in Ciudad Rodrigo to win the stage.
Roglic (Jumbo-Visma) finished second, collecting six precious seconds. He extended his overall race lead to 45 seconds on Richard Carapaz of Ineos Grenadiers, with only Saturday’s final mountain stage to race, before the Vuelta finishes in Madrid on Sunday.
Fulwood racer Carthy (EF Pro Cycling) is third overall at 53 seconds adrift of Roglic.
Cycling legend Alberto Contador earlier told Europsport that Carthy is the strongest rider in the race, but fears time may run out for the British rider to catch Roglic.