If the registered trademark is a design mark including words, should you use a (R) symbol when using the words in text?
Probably not. The registered mark is usually quite specific. A portion of the mark is not the registered mark.
The legal use of ® circle r is granted by statute. The registered mark is displayed and described with specificity in the trademark application. So, it follows that you would only use ® with the registered mark as described and displayed in the the registered trademark.