Roach was due to spend the opening two months of the season with Surrey but injured his hamstring during their innings win against Hampshire, the second game of his second stint with the club.
Alec Stewart, Surrey's director of cricket, spent much of last week's win against Somerset making phone calls to try and sort a replacement in time for their next Championship fixture against Gloucestershire in Bristol on Thursday.
His search has proved fruitful, with de Grandhomme due to play their next three Championship games on a short-term deal. Surrey will be his third county, following previous stints with Warwickshire and Hampshire.
"Following the injury to Kemar we are pleased to have secured Colin's services for the next three four-day games," Stewart said. "He already has good experience of the county game and will add to the quality and balance of the team."
Surrey will also be strengthened by the arrival of Dan Worrall
, the Australian seamer who has signed a three-year deal as a local player thanks to his British passport.
Worrall's arrival in the UK was delayed for family reasons, but he landed last week and was seen at The Oval during the Somerset fixture. He is set to make his debut against Gloucestershire, his former county.
Surrey are the early pace-setters in Division One and the addition of two new players to their squad will provide a timely boost. James Taylor
, the young seamer, did not bowl in the second innings against Somerset due to a back spasm, while Sam Curran
's workload is being managed carefully by the ECB as he returns to fitness following a stress fracture which ruled him out of England's winter.
Curran was allowed to bowl 15 overs across the Somerset fixture (10 in the first innings and five in the second), though went unused in the second after he batted for nearly three hours. "We didn't want to take any chances because he worked so hard throughout the winter after his injury and we have to follow the regulations," Azhar Mahmood, Surrey's assistant coach, explained.