The Rogues can be incredibly dangerous. The Weather Wizard alone has immense potential as a villain.
Make their "code names" either just their pet nicknames for each other, or something The Flash calls them to make fun of them, or distract them. And then they OWN those names, and make them terrifying.
The Rogues can be developed as a group, because the point is that they ARE a group. They function better as a group. The invidual characters don't require a lot of exploration in that sense.
I'd use Eobard Thawne in the first film, with hints at the rogues in the future, showing that being a "rogue" became a sort of calling for some criminals.
The Rogues would then feature in the second, dealing with technological weapons they have, and them using technology they don't quite grasp (Including time travel?). They could function as superterrorists, and threaten not only Keystone City, but the world.