It all depends what you are doing. You can regenerate an RT using either the "Generate" icon and select one of the top two options. Again you can use right click in the Main Tracks Window and select the same two options. Be wary of the song setup - if this is a BIAB importation then use Track > Make all BB tracks regular tracks before experimenting.

I have just tried regeneration of an RT and regenerated five separate audio clips within it. This worked satisfactorily.