Tag searching in resource files (.rs) use different tags-files, TAGSRS, than when tag searching cm-files.

In emacs:

• Visit tags table (C-c v), choose the file "TAGSRS" in the directory you want to search.
• Tags search (M-s) and type your regexp as usual.

In most cases, the files TAGSRS are already available in your workspace. If not, do this in a command prompt:
C:\CetDev\version10.5git\base>make rs-tags