\documentclass{scrartcl}
\usepackage{amsmath}
\usepackage[default]{gfsneohellenic}
\usepackage[scaled]{beramono}
\usepackage[LGR,T1]{fontenc}
\begin{document}
One two three.
\begin{itemize}
\item This is produced via the use of \verb+\text+: $\text{a}$.
\item This is produced with \verb+\mathrm+: $\mathrm{a}$.
\end{itemize}
\end{document}