Roberts founded Comcast when he bought a small cable television system in Tupelo, Mississippi in 1963, and was responsible for growing the company into a $150 billion media conglomerate.
Roberts, who was chairman emeritus of Comcast's board, had spent more than five decades at the company.
"Ralph was a born entrepreneur, a visionary businessman, a philanthropist and a wonderful human being," the company said in a statement.
Roberts died of natural causes in Philadelphia, Comcast said in a statement.
His son, Brian Roberts, is the chairman and CEO of the company.