# How to use roman numerals for backup slides on beamer?

I'm making a LaTeX presentation using beamer, and I'd like to prepare some slides for possible questions I can be asked for.

I find how to ignore slides numbering in this post, but I don't like the result, which is roughly the following:

Slide 1/n Slide 2/n...Slide n/n [from here questions slide] Slide (n+1)/n Slide (n+2)/n

What I would achieve is roughly the following:

Slide 1/n Slide 2/n...Slide n/n [from here questions slide] Slide I Slide II

How can I achieve it?

The following example:

\documentclass{beamer}
\setbeamertemplate{footline}[page number]

\defbeamertemplate{footline}{page number appendix}
{%
\hfill%
\insertpagenumber\kern1em\vskip2pt%
}
\makeatletter
\setbeamertemplate{footline}[page number appendix]%
\renewcommand*{\insertpagenumber}{%
}%
}
\makeatother

\usepackage{appendixnumberbeamer}

\begin{document}
\begin{frame}A\end{frame}
\begin{frame}B\end{frame}
\begin{frame}C\end{frame}
\appendix
\begin{frame}D\end{frame}
\begin{frame}E\end{frame}
\end{document}

has the following page numbers in the footline: 1/3, 2/3, 3/3, I, II.