I fly IL2 and there are open servers there such as =gRiJ=Dedicado and Spitz vs BF109.
These are dogfight servers
As indicated by Dart, there's no online dogfight mode in RoF, only a online cooperative mode (in witch you can only join at each mission start).
Online dogfight mode will be added later in a patch.
In Il2 also, you have 2 online mode, the dogfight (which server you can join any time), and cooperative (where you can't join once the mission is started)
And no... RoF can't work with hypperlobby, since it has its own server browser. Maybe later Jiri can add something for RoF access in Hypperlobby... I don't know if it's technically possible.