In DotImage 5.0, using DotAnnotate in WinForms application, you cannot freely rotate an annotation where the Translucent property is set to true.
The workaround is to use Transparent colors instead. You could set the colors to transparent colors (where the alpha channel is less than 255) all of the time, or handle the selection events and set it then (and set Translucent to false at the same time).
For example if you had this code:
anno.Translucent = true;
anno.Fill = new AnnotationBrush(Color.Blue);
anno.Outline = new AnnotationPen(Color.Red);
Change to this code:
anno.Translucent = false;
anno.Fill = new AnnotationBrush(Color.FromArgb(128, Color.Blue));
anno.Outline = new AnnotationPen(Color.FromArgb(128, Color.Red), 30);
It won't match the color exactly. One thing you might try to get closer is to use slighly darker versions of the colors in your replacement code.