Film rolls back automaticaly

The camera shouldn't be doing this, assuming you're using 36 exposure (or 24 exposure) film. You may want to set a custom function to prevent automatic rewind -- you would have to rewind the film yourself by pressing the rewind button.

To do this:
1. Under the palm grip, press the 'CF' (custom function) button.
2. Use the main dial to select 'F1' in the LCD. It should show a '0' below the 'F1'.
3. Press the 'CF' button to change the '0' to a '1'.
4. Press the shutter button half way to save the change and exit the custom function setting mode.

If you want to stop the rewind with the film leader still exposed (film doesn't rewind entirely into the cannister), use the same steps but set custom function 'F2' to a value of '1'.