Hi
For a horizontal rotation as per Borate's suggestion....
Place the image on the timeline and click the FX button
Click the down arrow next to the Add Effect tab and select ROTATE.
Slide the red cursor to the left.
Ensure that the value for the horizontal slider is set to 0 (or enter 0 into the box)
Click the centre green cross.
Slide the cursor to the half way point of the clip.
Slide the Horizontal slider to 90 (or enter 90 into the box)
Slide the red cursor to the extreme right (end of clip)
Move the slider along to read 180 (or enter 180 in the box.
Click the Apply button
When played, your image will now flip over by rotating on a vertical axis.
If you want the image to rotate in the opposite direction the values for the horizontal slider are:
360 at the start
90 for mid position
0 for the end of the clip.
Or you could apply the first settings above and then reverse the clip.
Is this what you were after?
Note: Your image will rotate with a black background. If you want a different background...colour...image..video etc... place your rotating clip on video track 2 with the background image/clip etc. directly under it on video track 1
Nat