Hello,
The only way I know of how to get the rotation to be an animaiton is using a macro. Here is a bit of code that will rotate an object 360 degrees and the DoEvents line will make PowerPoint reposition the shape each time so it looks like an animation. Hopefully you are working with 2007.

Public Sub CircleRotate()
Dim sld As Slide
Dim dude As Shape
Dim n As Integer


Set sld = ActivePresentation.Slides(1) 'slide number visual is on
Set dude = sld.Shapes("Picture 2") 'name found by using Selection Pane

n = 20
For i = 1 To n
If i < 10 Then
dude.Top = dude.Top + 1
dude.Left = dude.Left + 1
Else
dude.Top = dude.Top - 1
dude.Left = dude.Left - 1
End If
dude.Rotation = dude.Rotation + (360 / n)
DoEvents
Next i
End Sub

This will move the dude object in a line, for a circle you have to use four quandrants, so some adjustments will be needed.

Then to execute the code, you can assign an action to the shape you are trying to move. Once you have written the macro, click on the shape, go to the Insert tab and you should see "Action" under the Links menu. Click on that and the Action Settings menu box will come up. Click on the Run a Macro option button and choose the macro name from the drop down.

Hope this helps!!

Signed,
Math Nerd