roman numbers are easy!
the basic search set is [IVX]+ add, L, M if you are approaching 50 or 100 but that is rare
I've done a few books, with no problems.
find <p>([IVX]</p> etc .
you may need other stuff e.g. there could be a class="bold" bit -so inspect in code view.
copy the 1st instance ( chapter I) and replace I with the search set