Romero free kicks rescue El Salvador
The Soca Warriors took control with midfielder Carlos Edwards scoring from outside the penalty area in the seventh minute and Dwight Yorke, 37, converted a penalty 20 minutes later after a foul on Stern John.
The visitors were awarded another penalty early in the second half, John stepped up but fired his effort over the crossbar.
El Salvador made them pay as Romero floated the first free kick home in the 79th minute and repeated the trick in the fourth minute of injury time with the last kick of the game.
Yorke was then sent off after being given a second yellow card for dissent.
Both teams were playing their first game in the final stage of the CONCACAF qualifying competition.