His long day began in the familiar confines of the ornate marble-fronted Supreme Court building before he headed across the street to the U.S. Capitol to preside over the full opening session of the impeachment trial.
On home turf, Roberts, 64, oversaw back-to-back Supreme Court arguments in the morning. Roberts walked up to the mahogany bench, looking calm, and scanned the audience before taking his seat and donning his reading glasses. He appeared relaxed and engaged as the lawyers in front of him argued their cases before the nine justices.
Roberts welcomed each new attorney sworn in by the court clerk with a smile. And when the arguments began he listened closely, shifting his gaze periodically from papers before him to the lawyer who was speaking.
On two occasions, Roberts made quips that prompted laughter in the courtroom. The first case involved whether a convicted felon's sentence for illegal gun possession should be increased under a federal law based on his previous convictions for drug trafficking. The second was a fight between companies over whether their legal dispute should be heard by an Alabama court or an international arbitrator in Germany.
Roberts then shifted gears and changed venues, walking into the Senate clutching a couple of large binders.
Senators must decide whether to remove Trump from office after the House of Representatives impeached him last month on charges of abuse of power and obstruction of Congress arising from his request that Ukraine investigate political rival Joe Biden.
As expected, Roberts stayed in the background. Unlike at the court, his impeachment role - mandated by the U.S. Constitution - is largely ceremonial. It appears he wants to keep it that way.
Sitting at a dais in the Senate chamber, Roberts unobtrusively oversaw the process, asking lawyers for Trump and the Democratic-led House to speak when required, while granting motions to take recess breaks.
A rare reference to Roberts' day job came via Democratic Representative Adam Schiff, one of the House "managers" presenting the case against Trump.
Schiff urged the 100 senators in the Republican-majority chamber to take on the role of jurors, not to act as judges in an appeals court reviewing work already done by a lower court.
"You are not appellate court judges," Schiff said, before turning to Roberts. "OK, one of you is."