Sono arrivato a questo codice che soddisfa le mie esigenze
` \usepackage{parskip}
\setlength{\parindent}{1.8em}
\usepackage[rightlabels,dotinlabels]{titletoc}
\renewcommand{\thechapter}{\scshape\roman{chapter}}
\renewcommand\thesection{\arabic{section}}
\usepackage[explicit]{titlesec}
\newlength\mylena
\newlength\mylenb
\setlength\mylena{1.8em}
\setlength\mylenb{\dimexpr\textwidth-\mylena\relax}
\newcommand\PlaceNumber[1]{%
\makebox[\mylena][l]{#1}}
\titleformat{\chapter}[hang]
{\normalfont\fontsize{11}{13}\selectfont}
{}
{0em}
{\PlaceNumber{\scshape\thechapter}\parbox[t]{\mylenb}{\raggedright#1}}
\titleformat{name=\chapter,numberless}
{\normalfont\fontsize{11}{13}\selectfont}
{}
{0em}
{\PlaceNumber{}\parbox[t]{\mylenb}{\raggedright#1}}
\titleformat{\section}
{\normalfont\fontsize{11}{13}\selectfont}
{}
{0em}
{\PlaceNumber{\thesection}\parbox[t]{\mylenb}{\raggedright#1}}
[\vspace*{5pt}]
\titleformat{name=\section,numberless}
{\normalfont\fontsize{11}{13}\selectfont}
{}
{0em}
{\PlaceNumber{}\parbox[t]{\mylenb}{\raggedright#1}}
[\vspace*{5pt}]
\titleformat{\subsection}
{\normalfont\fontsize{11}{13}\selectfont\itshape}
{}
{0em}
{\PlaceNumber{}\parbox[t]{\mylenb}{\raggedright#1}}
{}
\titleformat{name=\subsection,numberless}
{\normalfont\fontsize{11}{13}\selectfont\itshape}
{}
{0em}
{\PlaceNumber{}\parbox[t]{\mylenb}{\raggedright#1}}
\titlespacing{\chapter}
{0pt}
{0cm}
{3cm}
\titlespacing{\section}
{0pt}
{2em}
{0pt}`