That roll doesn't necessarily indicate a loss of power in that engine.
Airplane was already coming down. Might just be going through the last stage of a stall.
Need to see much clearer pics. Was the prop feathered? Was it pilot input to avoid stuff on the ground? Ailerons don't appear to be at any significant angle, but again, need better pics.
It reminds me a bit of American Airlines Flight 191
https://en.wikipedia.org/wiki/American_Airlines_Flight_191
Hydraulic lines were damaged when the engine tore off, causing the flaps and slats to retract on one side. One wing stalled and the plane rolled knife edge.
For those who don't know, flaps are used to boost lift at low speeds, namely on takeoff and landing. They direct airflow downwards and slow air moving over the top of the wing.
I'm guessing something similar may have happened here. Though hydraulic systems today are supposed to have plugs preventing loss of pressure in the event of an emergency. I suppose icing is a possibility but I can't imagine it getting cold enough in Taiwan at low altitude.
Most stalls like this are recoverable. You dip the nose and to increase your airspeed. That's assuming the pilots were aware that was the issue. Planes are supposed to have a stick shaker that alerts the flight screw of a stall. There may be some training, medical, or procedural issues that hampered awareness.
You can see in the images prior to the crash that the port side prop is feathered, indicating the engine is not running. Though an engine loss on a twin engine plane is recoverable. I'm not familiar with the ATR-72, but multi-engine planes are supposed to have redundant power systems in case of a single engine loss.
I'm sure investigators will be looking at all of that.