I'm surprised nobody has added the standard tipa way as an answer, which is mentioned in the document you linked to and in egreg's comment. Since you seem to be doing phonetics to me (as opposed to someone who just wants to get this specific single character for unrelated reasons), I would suggest to use the standard way.
I'll provide two versions: One basic one, which uses the standard Computer Modern fonts, and one more advanced one (but more realistic imho) that uses the Latin Modern fonts, basically in the way that Alan Munn proposed in Combining lmodern and tipa.
% Computer Modern version
\documentclass{article}
\usepackage{tipa}
\usepackage{lipsum} % just for dummy text
\begin{document}
Text with \tipa\ can be inserted in two ways, either with the command
\verb+\textipa{...}+ or with the environment \verb+\begin{IPA}...\end{IPA}+.
The output is really similar; the command is like inline math \(1+1=2\):
\textipa{[a\;Ra:]}.
The environment is probably intended for longer consecutive blocks of IPA, which
constitute a paragraph of their own:
\begin{IPA}
[a\;Ra:]
\end{IPA}
This is typeset, however, pretty much like ordinary text.
This is different from a lot of environments that get extra space before and after,
as e.g.\ block math:
\[
1+1=2
\]
And this is just to show that there's extra space after our block math. Also,
it's centered.
\end{document}
If you want to use Latin Modern, the preamble could look like this:
% Latin Modern version
\documentclass{article}
\usepackage[utf8]{inputenc} % encoding of your .tex source file
\usepackage{lmodern} % Latin Modern font, basically an improved Version of Computer Modern
\usepackage[T3,T1]{fontenc} % font encoding in the pdf output
\usepackage[noenc]{tipa} % noenc because we've already used fontenc
% This is based on Alan Munn's excellent advice for tipa and lmodern
% https://tex.stackexchange.com/a/37087/4012
\newcommand\tiparmdefault{cmr}
\renewcommand{\textipa}[1]{{\fontencoding{T3}\fontfamily{\tiparmdefault}\selectfont#1}}
\renewenvironment{IPA}{\fontencoding{T3}\fontfamily{\tiparmdefault}\selectfont}{}
\usepackage{lipsum} % just for dummy text
The output of both versions looks extremely similar; here's a screenshot of the lmodern version:

\;Rworks inside\textipa:\textipa{\;R}or, outside it,\textscr. – egreg Oct 11 '12 at 12:59