"I didn't serve very well. It was unacceptable," American Roddick told a tense post-match news conference after losing to the South African.
The 29-year-old American then snapped at a Chinese reporter who asked him if he was considering retiring.
"I think you should retire," he said before abruptly leaving the media room.
Roddick's exit has left the tournament low on crowd-pulling names after French Open champion and local favourite Li Na's shock first-round loss on Sunday and the withdrawal of several top players, including world number two Maria Sharapova.
Defending men's champion and world number one Novak Djokovic pulled out two days before the start of the tournament because of a back injury.