"Unfortunately it was probably the wrong call," Robshaw told BBC Sport.
"You have to judge every game as it comes and get a feel for it. That falls on my head. At the end of the day, I have to make those decisions."
Matt DawsonFormer England rugby international
"It's just given the media an unbelievable story. That one decision has said to the public 'we don't know how to lead this side; we are not making the right decisions at the right time'. Two minutes to go, you know [South Africa] are going to take an eternity to walk back. I just can't get my head round it. It's baffling. It's a kick to the corner and have a go at driving to the corner."
Last week England were criticised for spurning two kickable penalties in the second half of their defeat by Australia, with Robshaw instead opting to go for touch on each occasion.
His decision-making has now been criticised again, with former England scrum-half Matt Dawson describing the decision to kick at goal with so little time left as "baffling".
Robshaw explained his thinking after the match. "There were a couple of minutes on the clock and we thought we had enough time to get down there again and potentially get ourselves in drop-goal range," he said.
"We didn't take the restart and didn't quite get in range again and it allowed them to close out the game.
"We were playing well, putting them under pressure, they were giving a lot of penalties away, but it probably wasn't right. Unfortunately it just wasn't to be."
Lancaster frustrated by narrow defeat
England coach Stuart Lancaster refused to comment on Robshaw's decision in the immediate aftermath of the match.
"I think we need to review all our decisions. I am not going to comment on individual decisions," he said.
Lancaster said he wanted to focus on the positives.
"We pushed them to the line and we should have got over the line but we couldn't," he added.
South Africa captain Jean de Villiers said: "We wanted three wins so we are pretty happy tonight. Earlier in the year, we probably would have lost this game."
Meanwhile, fly-half Toby Flood was cleared of a broken toe after undergoing an X-ray in the wake of the defeat, yet remains a doubt for England's final QBE autumn Test against New Zealand next Saturday.
Flood's injury will be reassessed by the England medics on Sunday evening, when a decision over the need for any further scans will be taken.
"It doesn't look great," Flood wrote in his column for the Mail On Sunday.
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