\documentclass{rapportECL}
\usepackage{lipsum}
\usepackage{enumitem}
\title{Rapport ECL - Template} %Titre du fichier
\usepackage{pdfpages}
\usepackage[T1]{fontenc}
\usepackage{newcent}
\renewcommand{\familydefault}{\sfdefault}
\usepackage{color}
\usepackage[explicit]{titlesec}
\usepackage{multirow}
\titleformat{\section}
{\color{bleu_challenge}\Large\sffamily}
{}
{0em}
{\fcolorbox{bleu_challenge}{orange_challenge}{\parbox{\linewidth-7pt}{\vspace{0.3cm}\hspace{0.4cm}\Roman{section}. #1 \vspace{0.3cm}}}}
[]
\titleformat{name=\section,numberless}
{\color{bleu_challenge}\Large\sffamily}
{}
{0em}
{\fcolorbox{bleu_challenge}{orange_challenge}{\parbox{\linewidth-7pt}{\vspace{0.3cm}\hspace{0.4cm} #1 \vspace{0.3cm}}}}
[]
\begin{document}
%----------- Informations du rapport ---------
\titre{Rapport Challenge}
\datedoc{Date du rapport}
\logoasso{logos/logo.png}
%----------- Initialisation -------------------
\fairemarges %Afficher les marges
\fairepagedegarde %Créer la page de garde
\tabledematieres %Créer la table de matières
\pagesignatures{}{}{}{}{}{}{}{} %Inserer {Nom du signataire 1}{Poste du signataire 1}{Signataire 2}....
\renewcommand{\thesection}{\Roman{section}}
\renewcommand{\thesubsection}{\arabic{subsection}.}
\newcommand{\sectiontoc}[2][\thepage]{%
\stepcounter{section}%
\contentsline{section}{\thesection\hspace{1em}#2}{#1}}
\newcommand{\subsectiontoc}[2][\thepage]{%
\stepcounter{subsection}%
\contentsline{subsection}{\thesubsection\hspace{1em}#2}{#1}}
%------------ Corps du rapport ----------------
\section*{Introduction}
\section{Partie I}
\section*{Conclusion}
\end{document}
