Hi, let me preface this by saying that if all the things you are saying are 100% accurate (and I'm not going to investigate right now), that your assumptions are also correct.
Therefore, if you are to take on this task, ROO should be in the Note field of the base set and it's parallels. TC should only be used in the base set.
As for putting it in the ste's Glossary - Once you use the abbreviation, the entry is automatically added to the set's Glossary. In this case, "ROO" would not be automatically defined, so you will have to click on the Dlossary link in the list of links on the left side, and there will be a link to "edit" in the definition area for "ROO" where you can enter "Rookies" (which is different from "RC = Rookie Card").
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 10/25/2023). I have added a large portion of my inventory to the site, and currently have trading turned off (details are in my profile). I have (finally) unearthed my 2 very large boxes of Star Company minor league sets and they are available (email for details).