You could also use the JavaObject library to rotate the ImageView.
B4X:
'Sets the rotation angle of the given view
'v = view
'Angle = rotation angle in degrees
Sub setRotation(v As View, Angle As Float)
Dim jo = v As JavaObject
jo.RunMethod("setRotation", Array As Object(Angle))
End Sub
I don't remember when this was addaed, in older Android versions, like 2.3, it wont run.