Between 1994 and 1995, Roberts anchored the daily newscasts at 5 p.m. and 11 p.m. for CBS's flagship station in New York. His next role was to anchor "CBS Sunday Evening," and he spent the next 11 years of his career in that role. In 1999, Roberts anchored the "CBS Saturday Evening News" and became the chief correspondent from the White House for CBS. He continued this role until 2006. In 2003, Roberts was embedded with the 2nd Light Armored Reconnaissance Battalion of the U.S. Marines during the initial invasion of Iraq. In February 2006, Roberts left CBS to join the CNN network. He reported from war zones such as the Israel/Hezbollah war front lines and was also embedded with an Israeli infantry unit. From 2007 to 2010, Roberts was the co-anchor of the CNN morning program "American Morning." He left the program to stay closer to his fiancée, Kyra Phillips, another anchor for CNN in Atlanta. In January 2011, Roberts started working for Fox News as a national correspondent based in Atlanta and as the Chief White House Correspondent.

Roberts has provided the public with exceptional coverage and breaking news such as the Presidential debates, Hurricane Irene, and the Republican National Convention. John has traveled to many international destinations to cover the news. He traveled to Yugoslavia during the NATO Bombing in 2005, and he was also present to capture the earthquake that occurred in Turkey. He has interviewed and met many interesting personalities, including former Presidents George W. Bush and Bill Clinton.