Still Stevenage were not finished and Roberts hit the crossbar when he met a corner, but when Defoe ran on to a Bale throw-in to score his second and the match was over.
Redknapp replaced Rafael van der Vaart with Roman Pavlyuchenko and the Russian was twice thwarted by Green before the England goalkeeper pulled off a world-class save to push Bale's set-piece on to the bar.