org-roam/doc/org_export.md

To include the backlinks in your Org file export -- whether using Org's in-built publishing or ox-hugo -- use the following snippet to add a "Backlinks" section at the end of the page:

(defun my/org-roam--backlinks-list (file)
  (if (org-roam--org-roam-file-p file)
      (--reduce-from
       (concat acc (format "- [[file:%s][%s]]\n"
                           (file-relative-name (car it) org-roam-directory)
			                     (org-roam--get-title-or-slug (car it))))
       "" (org-roam-sql [:select [file-from] :from file-links :where (= file-to $s1)] file))
    ""))

(defun my/org-export-preprocessor (backend)
  (let ((links (my/org-roam--backlinks-list (buffer-file-name))))
    (unless (string= links "")
      (save-excursion
      	(goto-char (point-max))
      	(insert (concat "\n* Backlinks\n") links)))))

(add-hook 'org-export-before-processing-hook 'my/org-export-preprocessor)