The 25-year-old has yet to play a Test, with his international experience limited to nine one-day games and three Twenty20 matches.
Rossouw is currently nursing a finger injury so Temba Bavuma could be in line to make his Proteas debut in Port Elizabeth.
Wicketkeeper De Kock injured his left ankle while warming up before play on the third day of the first Test at Centurion, a match South Africa wrapped up by an innings and 220 runs on Saturday.
AB de Villiers is now set to keep wicket for the hosts in the second Test which starts on Boxing Day.
Meanwhile, the West Indies have called up left-arm fast bowler Kenroy Peters as a replacement for Kemar Roach.
Roach injured his right ankle while bowling on the first day of the first Test and has been ruled out of the rest of the series.
Peters, 32, has so far taken 190 wickets in 62 first-class matches.