Roger has a special place in his heart for female Quidditch players, so he's pretty fond of Katie as far as playing with her goes. That doesn't mean he'll go any easier on her, but he'll flash a smile her way whenever he steals the Quaffle.
Pre-Fleur, Roger definitely would have been all over that. Post-Fleur, he's secretly terrified that the Beauxbatons girls are all reporting on his actions, so he's not likely to go any further than some casual flirting.