Stuart Lancaster's side fell behind after Wesley Fofana scored a first-half try but put in a strong second-half performance to run out 23-13 winners at Twickenham.
"We were a little bit slow coming out of the blocks," Robshaw told BBC Sport.
"Our defence in the first half was pretty sloppy. Once we sorted that out it was pretty good."
England hopes a Grand Slam are very much alive heading into the final two games of the competition where they will face Italy and Wales.