The label is rotated around its centre after any transformations due to RotateModeWithImage have been applied.
This property only applies to labels of type rectangle, ellipse and text
If RotateTextWithImage is true, and the label is of type text, then:

For display, this angle is added to the rotation of the image.
 This angle is modified when Rescale is called, so as to preserve the relationship between the text and the image

DicomLabel Object  | DicomLabel Members