\documentclass[a4paper]{article}
\usepackage{lmodern}
\usepackage{amssymb,amsmath}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{hyperref}
\usepackage{enumitem}
\begin{document}
\thispagestyle{empty}

\begin{enumerate}[label=\roman*]
  \item first item
  \item second item
  \item third item
\end{enumerate}

\begin{enumerate}[label=\arabic*]
  \item first item
  \item second item
  \item third item
\end{enumerate}

\begin{enumerate}[label=\alph*]
  \item first item
  \item second item
  \item third item
\end{enumerate}

\end{document}
