I had oscillation in pitch when doing fixed wing with CC3D a long time ago.
One solution is to reduce your roll PID (reduce both P and I by the same multiplicative factor, like multiply both by 0.75) until the fastest flight speed you use does not oscillate. That leaves it a bit slower to respond than it could be when you are flying slowly, but it works.
The best solution is to use an airspeed sensor so the PIDs can be reduced automatically at high speed. I don't remember whether CC3D supports airspeed sensors, or whether you need a Revo class FC to do that.