A torque converter is a pump, a pump that couples the engine to the transmission using fluid pressure while the engine is turning faster than the transmission input (I am not talking about lockup clutches because they don't engage if shut down or not moving fast enough). If you keep your engine running and do not rev the engine, depending on the stall speed of your TC you can (and most likely will) roll backwards when you put the transmission in a forward gear, same for rolling forward in reverse. The vehicle will roll both directions in either gearing, but rolling forward probably isn't noticeable in drive or rolling backwards in reverse because a person is expecting that type of motion. This is why you hear people say you can't push/bump start a vehicle with an automatic transmission.
With the engine off it is the same, no fluid pressure between them so nothing to couple the engine to the transmission. Unless something is in place in the transmission (the small parking lock pin) or after (parking/emergency brake) the vehicle will move when a force is applied (either through gravity or pushing), engine compression will not help.
Sorry
, poor joke, Anton Yelchin just passed away after being crushed between his house and his (here's the irony) Jeep when it wasn't put properly into park and he was caught between it and his garage when it rolled. He had a newer Grand Cherokee with some odd quirk that made it hard to properly place the transmission in park - which is why a parking/emergency brake should always be used,one should never rely on the parking lock pin to hold a vehicle, especially on an incline.