Minimal working example:
\documentclass{report}
\usepackage{titlesec}
\usepackage{titletoc}
\titleclass{\part}{top}
\titleformat{\part}[display]
{\centering\normalfont}
{\itshape \partname~\thepart}{1.0em}
{\bfseries\MakeUppercase}
\titlespacing*{\part}{0pt}{0pt}{20pt}
\renewcommand{\thechapter}{\Roman{chapter}}
\dottedcontents{section}[5.0em]{}{3.5em}{0.75pc}
\begin{document}
\startcontents[parts]
\part{Part I}
\printcontents[parts]{}{0}{}
\chapter{Chapter I}
\section{Section I.1}
\chapter{Chapter II}
\section{Section II.1}
\chapter{Chapter III}
\section{Section III.1}
\stopcontents[parts]
\end{document}
Problem: add space between the bold Roman numerals and words (for chapters) in the table of contents.
\titleclass{\part}{top}command from thetitlesecpackage for your first problem.\partby default enforces a page break in thereportdocument class. – Troy Mar 25 '17 at 08:27titletocpackage.\printcontentstakes in one optional argument in square brackets and three mandatory arguments in curly brackets. What you have in your MWE is four curly brackets, and so it produces an error. – Troy Mar 25 '17 at 08:31\vbox{...}around the part and the\printcontents. This should prevent the pagebreak. With this approach you don't change the behavior of\parton other occasions. – Skillmon Mar 25 '17 at 08:40\printcontentscommand is thename, which you need to pass to\startcontentsand\stopcontentsas well, but this is only used if you want to have multiple TOCs.. (Read the documentation if you want to know more). If you only have this one, then try this:\printcontents{sections}{0}{}– Troy Mar 25 '17 at 08:41[]I get an error "No partial toc named ." – Skillmon Mar 25 '17 at 08:43\dottedcontentsto fix the chapter spacing – Randy Randerson Mar 25 '17 at 09:15\dottedcontents{section}[0em]{}{3.2em}{1pc}– Skillmon Mar 25 '17 at 09:19\dottedcontents{chapter}[1.0em]{}{3.0em}{}change it to\dottedcontents{chapter}[1.0em]{\bfseries}{3.0em}{0pc}. This also solves the non-bold chapters. – Skillmon Mar 25 '17 at 09:30