Where can I download flight data containing pitch, roll and yaw angles?
FlightRadar 24 has an API that you can get data from. This is only from aircraft with ADS-B transponders, so it excludes some smaller and older planes. This would indirectly:


Give you points with which you could calculate the turns.
Give you pitch as the rate of climb.


This might give you a bigger but less exact dataset. Unfortunately, you might be disappointed in that normal commercial aircraft make relatively few manoeuvres at cruise.

Depending on the sort of simulations you might find that making a simulated flight in FlightGear (Open Source Simulator) might yield better results. If memory serves me right there is some equivalent to a flight data recorder so you can pull the data when you are finished.