Btukfyl

Can you please help me write an enumerated list which is in the same line and there is no line change between that and the rest of the text. E.g.,

We use three broad geographical regions, i.e., (i) the U.S., (ii)
current EU-27 countries, and (iii) all remaining countries.

With enumitem it is easy.

documentclass{article}

usepackage[inline]{enumitem}

begin{document}

  We use three broad geographical regions,

  begin{enumerate*}[label=(roman*),before=unskip{ i.e., }, itemjoin={{, }}, itemjoin*={{, and }}]

  item the U.S.

  item current EU-27 countries

  item all remaining countries.

  end{enumerate*}

end{document}

This is a little late to the party but another solution that is really clean and easy to use is the paralist package.

A quick example of it:

documentclass[11pt]{article}

usepackage{paralist}

begin{document}

This includes:

begin{inparaenum}[(i)]

item first task,

item second task and

item third task

end{inparaenum}

to be completed by the end of the month.

end{document}

This will come out as:

This includes: (i) first task, (ii) second task and (iii) third task to be
completed by the end of the month.

More can be found here
https://texblog.org/2013/02/01/inline-lists-in-latex-using-paralist/