Let us see the following code:

```
\documentclass{article}
\begin{document}
\newtheorem{theorem}{Theorem}
\begin{theorem}
TFAE
\begin{itemize}
\item[(i)]
$0<1$;
\item[(ii)]
$1>0$.
\end{itemize}
\end{theorem}
But I want (i)'s Roman:
\begin{theorem}
TFAE
\begin{itemize}
\item[\textrm{(i)}]
$0<1$;
\item[\textrm{(ii)}]
$1>0$.
\end{itemize}
\end{theorem}
Alas, still italic, but\ldots
\begin{theorem}
TFAE
\begin{itemize}
\item[\rm(i)]
$0<1$;
\item[\rm(ii)]
$1>0$.
\end{itemize}
\end{theorem}
\end{document}
```

And `\textrm`

, which should be better than an obsolete `\rm`

(I know the differences of using them) doesn't work as one can expect. Is it an argument for using `\rm`

from time to time?

## Best Answer

No,

`\rm`

is deprecated and should not be used in a LaTeX2e document (ConTeXt and plain are of course different). What is happening here is deliberate. Issuing`\textrm`

means that the current font family should be roman, not sanserif or monospaced. However, it doesnotalter the current shape (upright/italic/slanted) or weight (light/medium/heavy): that's the entire point of the LaTeX2e 'New Font Selection Scheme'. In contrast,`\rm`

sets a fixed font: upright, roman, medium weight.What you therefore are looking for here is altering the font shape, not the family:

`\textup`

is the command you are after (cf.`\textit`

,`\textsl`

). Of course, in a real case you should be applying this as an change to the general theorem style not just on anad hocbasis.