image-dired-cmd-rotate-original-options

image-dired-cmd-rotate-original-options is a variable defined in `image-dired.el'.
Its value is

"%p -rotate %d -copy all -outfile %t \"%o\""

Documentation:
Format of command used to rotate original image.
Available options are %p which is replaced by
`image-dired-cmd-rotate-original-program', %d which is replaced by the
number of (positive) degrees to rotate the image, normally 90 or
270 (for 90 degrees right and left), %o which is replaced by the
original image file name and %t which is replaced by
`image-dired-temp-image-file'.

You can customize this variable.