Following @yiannis-lazarides comment here, I decided to use the modroman package for my frontmatters.
In my actual project I don't have that many references, and thus decided to use the thebibliography environment.
The problem is that I'm also using hyperref with the pagebackrefs option enabled, and this gives me some very strange warnings; not strange because of the warning per se, but rather because of when it happens (which baffles me).
The warning itself is:
name{page.xiij} has been referenced but does not exist, replaced by a fixed one
and its raised when LaTeX is typesetting the pagebackrefs in question.
A minimal working example (exercising the warnings further) follows:
\documentclass{book}
\usepackage[pagebackref]{hyperref}
\usepackage{modroman}
\begin{document}
\frontmatter
\renewcommand{\thepage}{\texorpdfstring{\modroman{page}}{\roman{page}}}
\setcounter{page}{10}
Lorem ipsum dolor sit amet\cite{bib}, consectetur adipiscing elit.\clearpage
Lorem ipsum dolor sit amet\cite{bib}, consectetur adipiscing elit.\clearpage
Lorem ipsum dolor sit amet\cite{bib}, consectetur adipiscing elit.\clearpage
Lorem ipsum dolor sit amet\cite{bib}, consectetur adipiscing elit.\clearpage
Lorem ipsum dolor sit amet\cite{bib}, consectetur adipiscing elit.\clearpage
Lorem ipsum dolor sit amet\cite{bib}, consectetur adipiscing elit.\clearpage
Lorem ipsum dolor sit amet\cite{bib}, consectetur adipiscing elit.\cleardoublepage
\begin{thebibliography}{9}
\bibitem{bib}
A.~N.~Author.
Some title here.
\emph{Another one here}, (12):3--5,
September 1990.
\end{thebibliography}
\end{document}
Thoughts anyone? :)