The rotate function is off by default. Click on the asset lane to turn it on. The checkbox for Rotate applies a clockwise rotation to all animation options above. Per default, this rotation is set to 3 degrees and starts from 0 degrees rotation.
You can change the rotation settings under "Properties" if you need to.
Note: When rotating an asset, regardless of which animation you have chosen, the rotation will also apply a scale on the asset to make sure that it always fills the format. This "rotation scale" can in extreme cases of rotation actually counteract your chosen animation in certain parts of the animation. This is not necessarily bad since it can create cool animations. Use the slide preview to check that out.