I'm encountering the same problem as in "roman numbers too wide in table of contents" and in "In table of contents, long page numbers intrude on right margin despite plenty of available space".
I'm not to sure about the solutions presented there. As I use KOMA-Script, I preferred using tocstyle, but the package happily announces:
THIS IS AN ALPHA VERSION! USAGE OF THIS VERSION IS ON YOUR OWN RISK! EVERYTHING MAY HAPPEN! EVERYTHING MAY CHANGE IN THE FUTURE! THERE IS NO SUPPORT, IF YOU USE THIS PACKAGE! Maybe it would be better, not to load this package
Maybe it really would be better not to use tocstyle.
In another answer, I read that tocloft doesn't work well with KOMA-Script. So this is doesn't sound like an alternative either.
The other answer to these questions redefines \@pnumwidth. As I have no knowledge of the LaTeX kernel, I'm not sure whether this changes too many widths.
So my question is, is there a good, stable solution to roman numbers intruding into the margin? Or are any of my concerns with the proposed solutions wrong?
For reference, here's a MWE:
\documentclass{scrreprt}
\begin{document}
\pagenumbering{Roman}
\tableofcontents
\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
\chapter{Chapter}
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
Text\clearpage
\section{Section}
Text\clearpage
\section{Section}
\end{document}
And it's result (The margin begins at the last "I" in "XIII"):

tocstyle) is safe to use. Be brave and do it ;-) – Johannes_B Jan 31 '16 at 15:35arabicnumerals all along the document would be the most simple solution. On the other hand, some people stick to old methods like grabbing a tree in a hurricane. – Johannes_B Jan 31 '16 at 15:38(see also page VI)... not only is that quite ugly, but the reader does not know, if page VI is in the front or the backmatter. The guys in the thesis office are thehurricane guys. – Johannes_B Jan 31 '16 at 15:47