What bibtex fields can be inserted into reference notes via the orb-templates.  What I’m calling a “bibtex field” are, for example, citekey and title in the template below:
(setq orb-templates
  '(("r" "ref" plain (function org-roam-capture--get-point) ""
     :file-name "${citekey}"
     :head "#+TITLE: ${citekey}: ${title}\n#+ROAM_KEY: ${ref}\n" ; <--
     :unnarrowed t)))
I tried to put year in my template but this had no effect.  Should it?  How about abstract?