Consider the following MWE
\documentclass{beamer}
\setbeamertemplate{frametitle continuation}[from second][
\insertcontinuationcountroman]
\usepackage{lipsum}
\begin{document}
\begin{frame}[allowframebreaks]
\frametitle{Foo}
\framesubtitle{Bar}
\lipsum[1]
\framebreak
\framesubtitle{Baz}
\lipsum[2]
\end{frame}
\end{document}
As it can be seen in the image, the first frame has the proper title, Foo, but the wrong subtitle (it should be Bar instead of Baz). How I can fix this? I know that for the second frame I can just create a new frame like this:
\begin{frame}[allowframebreaks]
\frametitle{Foo II}
\framesubtitle{Baz}
\lipsum[2]
\end{frame}
and avoid my current problem. However I was wondering if it is possible to place an explicit frame break with a new subtitle for the continuation frame without resetting the subtitle for the first frame.

Edit After @Mark showed me this question I can do this:
\documentclass{beamer}
\begin{document}
\begin{frame}
\frametitle{Foo}
\only<+>{
\framesubtitle{Bar}
}
\only<+>{
\framesubtitle{Baz}
}
\end{frame}
\end{document}
to get the correct subtitles in each frame. The problem with this approach, as seen in the image, is that I want the title on the second frame to be Foo II instead of Foo (I like the allowframebreaks behavior of showing a roman numeral appended to the title of a continuation frame).
So my question is, can I use the overlay approach to fix the subtitle reset problem but also somehow append roman numerals to the titles of the continuation frames as allow allowframebreaks does?
