Roberts was raised in Indiana and received undergraduate (1976) and law (1979) degrees from Harvard University, where he was the managing editor of the Harvard Law Review. From 1980 to 1981 he served as a law clerk to Supreme Court (Supreme Court of the United States) Justice William H. Rehnquist (Rehnquist, William), who later became chief justice. President Ronald Reagan appointed Roberts special assistant to Attorney General William French Smith in 1981, and the following year he became associate counsel to the president. He later worked at the law firm of Hogan & Hartson LLP in Washington, D.C., from 1986 to 1989, when he became deputy solicitor general in the administration of President George H.W. Bush (Bush, George). In 1992 Bush nominated him to the U.S. Court of Appeals for the District of Columbia Circuit. His nomination, however, died in the Senate, and the following year he returned to Hogan & Hartson. In his various roles, Roberts argued nearly 40 cases before the Supreme Court, winning 25 of them.

In 2001 Roberts was reappointed to the D.C. Circuit Court of Appeals, this time by President George W. Bush (Bush, George W.), and his bid again stalled. Bush resubmitted his name in 2003, and later that year he was finally confirmed by the Senate. Among Roberts's noted opinions was his dissent in Rancho Viejo v. Norton Gale (2003), in which a real-estate developer had been ordered to remove a fence that threatened an endangered species of toad. The court declined to hear the case, but Roberts questioned whether the Constitution's commerce clause, which ostensibly gave the federal government the authority to enforce such an order, applied. Some legal scholars interpreted Roberts's opinion as a challenge to the Endangered Species Act and other environmental protection laws. Roberts served on the circuit court until 2005, when Bush nominated him to fill the vacancy left on the Supreme Court by the retirement of Justice Sandra Day O'Connor (O'Connor, Sandra Day), whom he had helped prepare for her confirmation hearings in 1981. Shortly before Roberts's confirmation hearings began, Rehnquist died, prompting Bush to appoint Roberts chief justice. Roberts received bipartisan support, though some senators were troubled by his apparent advocacy of strongly conservative legal viewpoints as counsel in the Reagan and Bush administrations and by his refusal to provide specific answers to questions about his positions on various issues, including civil rights and abortion. The latter issue was a matter of particular concern to those who wondered whether Roberts's judicial decisions would be inappropriately influenced by his strong Roman Catholic faith. Quickly confirmed by the Senate (78–22), he was sworn in on September 29, 2005.