Glabus leaves on 5 January to become head of industrial and environmental policy at parent company the Volkswagen Group in Berlin.
Roberts, a former comms director at Mercedes-Benz UK, will report directly to Bentley Motors chairman and CEO Wolfgang Dürheimer, who said: "I am delighted to welcome Andrew Roberts into the Bentley leadership team as director of communications.
"Bentley is entering a key period of product launch and I am very confident Andrew will lead our communications team with the necessary experience and drive to deliver our goals.
"I would also like to thank Wolfgang Glabus for his contribution over the last couple of years which have brought record results for Bentley Motors and wish him continued success in his new role."
Roberts joined Bentley in 2012. Before this, he held a number of senior communications roles at Land Rover spanning nine years.
