It just took me several hours to figure out how to draw a circle or ellipse using the SDK.  If this saves you some time, send likes!

            Dim Anno As RectangleAnnotation = New RectangleAnnotation()
            Anno.Style = BoxStyle.Ellipse

That's it. Start with the Rectangle Annotation Class and set the style. If the rectangle is a square you'll get a circle, otherwise it's an ellipse.

You can set all of these other properties as well. Simple enough, yet there was nothing in Answers on this topic.