WASHINGTON - Supreme Court nominee John G. Roberts Jr. worked behind the scenes for a coalition of gay rights activists, and his legal expertise helped them persuade the Supreme Court to issue a landmark 1996 ruling protecting people against discrimination because of their sexual orientation. Then a private lawyer in Washington specializing in appellate work, Roberts helped represent the gay activists as part of his pro bono work at his law firm. He did not write the legal briefs or argue the case before the high court; he was instrumental in reviewing the filings and preparing oral arguments, several lawyers...