Scrum-half Ben Youngs remains a serious doubt as well, as does prop forward Alex Corbisiero.
But rather than worry about the difficulties of facing Fiji, Australia, South Africa and New Zealand without a few first-team regulars, Robshaw reckons it could boost England's chances of success when they host the next global gathering in 2015.
"Foden and Croft are both in the leadership group with responsibility in the squad, so of course they will be massive losses to the side," said Robshaw.
"But it gives an opportunity to someone else to come in.
"The likes of Mike Brown and Alex Goode are both playing very well at the moment and I'm sure there will be other players who will push their credentials as well.
"Unfortunately, injuries are something that happen in our sport and we have to be able to react and have faith in the players coming in, not just to do a good job but do a great job and put pressure on another player to get back in the side.
"That's what you want in the squad. If you look at New Zealand, if they have a couple of injuries they might go two players deep and still have world-class players in that position who come in and do a great job.
"That's where we want to be as a national side - to have two or three quality international players in every position."
Robshaw led England to four wins in a promising first Six Nations under new head coach Stuart Lancaster and the Red Rose then followed that up with a draw in the third Test against the Springboks this summer.
And while he admits winning the 2015 World Cup is the ultimate aim for everyone involved with England, Robshaw insists beating the very best right now is still hugely important.
"We've been to South Africa now and we've been to various countries in Europe as well, learning and taking little points out of those games," added Robshaw at the launch of England's new kit.
"There have been a lot of positives we can take from our performances, but also weaknesses which we have to eradicate. Hopefully we can be a bit more experienced, a bit wiser and do that now.
"Of course the end goal is the 2015 World Cup - we all know where we want to be then and what we want to achieve - but it's also about the here and now.
"We want to win every game but we have to break that down and work out how we're going to do that. In the autumn series, I don't think one game plan will apply to two opposition teams, let alone all four, so we do have to learn and adjust quickly."