I’m no massive authority but from what I know (I have the S2 Roadster 2008) the Roadster Sport was the launch model for the Series 3 engine in 2010

Same ‘Escape’ USA engine as the S2 but uprated in power

Other differences were slightly wider front axle and wider exhaust manifold

2008 XXVII Platform, Bugatti Blue Roadster 4 Seater