You want to make sure that text will continue to display even when it is rotated.
Use embedded fonts.
Unless you specifically use an embedded font, text fields use device fonts. For most situations, this is perfectly workable. However, in situations in which you want to animate a text field (or its parent movie clip) by changing its _rotation property, you must use embedded fonts. Device fonts will disappear in a rotated text field.
Recipe 8.20 explains how to embed fonts.