I think you've probs with the missing selector, right?! Well, I use GMenu, which creates a link between the gpe and the roms (=a build in selector). You have to name the roms specificially: the name must be under 20 letters (I think ... ) and the ending must be ".ngp" (the ngpcolor roms, too)!
But I got a question myself: Can you scale the game up to fullscreen?? 'Cause I miss this feature <_< .
stay cheesey