Roy suffered a back injury in the pre-session warm-up and is set to undergo a fitness test on Tuesday which will decide his participation in the first ODI.
South Africa have also been hit by injury concerns once again with all-rounder Albie Morkel ruled out of the first game due to back spasms.
Morkel picked up the injury while playing for the Titans in the domestic One-Day cup and South Africa have called up David Wiese as a cover.
With Dale Steyn and Vernon Philander already ruled out of the series and Kyle Abbott set to miss the first two games, South Africa have a depleted pace attack for the ODI contest.
Nevertheless, all-rounder JP Duminy reckons that the players who have been picked to take the place of the injured cricketers are capable of performing well.
Duminy is also drawing confidence from the fact that South Africa have won their last two bilateral ODI contests but is aware of England’s impressive form in the 50-over format.
“I don’t think we’re weakened,” said Duminy.
“I think the replacements are good enough to stand in for those players.
“It’s not an interruption in any way for us.
“We know what’s needed as a squad and it’s important for us to stay unified as a team, no matter who the personnel are.
“The confidence from the one-day cricket point of view has been pretty good.
“We’ve won our last two series.
“But we know this is a tough challenge that faces us and that England have also been playing really well in this format.”
To bolster their pace attack, South Africa have included Marchant de Lange in the squad and the team’s head coach Russell Domingo is confident that the 25-year-old will add depth to their bowling.
Domingo also dwelled upon the heavy workloads Kagiso Rabada and Morne Morkel have had in the recent past and indicated that the duo will be given a rest at some point in the series.
“Marchant gives us more options with our fast bowlers because there is no (Dale) Steyn, no (Vernon) Philander, no (Kyle) Abbott," said Domingo.
“The big concern is the fact that Kagiso Rabada and (Morne) Morkel have played a lot of cricket of late and have bowled so many overs, we need to manage them over the next few days.”
It has been more than 10 years since South Africa last won a bilateral ODI series against England, with their most recent victory coming in the seven-match contest held in 2005.
© Cricket World 2016