The report on the former archbishop of Washington, Theodore McCarrick, who was defrocked last year, states that Popes John Paul II and Benedict XVI were aware of the accusations of sexual misconduct.
The surprise move is seen as a rebuke to Pope Francis, who is weighing whether to allow older, married men to be ordained in some South American countries, where a shortage of priests is acute.
Oscar Romero was gunned down in 1980 after he denounced a crackdown by El Salvador's junta on its left-wing opponents at the start of a 13-year civil war.
On the second day of their conclave, 115 Roman Catholic cardinals settled on their selection. Now, the new pontiff faces the challenge of leading a church that is confronting many challenges. His chosen name honors a saint known for works of mercy and a simple lifestyle.