Translator's notes, prefaces, and introductions are numbered using Roman numerals so those pages can be safely cited without duplication or ambiguity.
It is customary to number the primary text with Arabic numbers starting at 1. But as the front matter is clearly 'before' page 1, you have to make accommodations for it in your numbering scheme. A new set of independently numbered Roman numerals are used to differentiate the two groups of pages. This allows both sets to 'start' at 1 (or i) without duplication. Also note that Roman numerals are always italicized. In contrast, end matter tends to continue the numbering of the primary text. Sometimes end matter is not numbered because it is short, rarely cited, or can be referenced in another way (i.e. 'footnote 31', or 'appendix A', or 'postscript').
There are some quite old standards for the ordering of front and back matter: Book design | Wikipedia. This Wikipedia page is the most comprehensive list of these rules that I've found online. However, some of these rules are more rigid than others so you can stray from them if you have a compelling reason specific to your project.
An excellent guide to print design is Bringhurst's book The Elements of Typographic Style. It is an authority for designers and commonly recommended as an introduction. It has a fair bit of history and explanation as to why these rules exist, but is mostly for designers and typographers.
If you just want formatting 'rules' beyond the Wikipedia page, then see Turabian's A Manual for Writers of Research Papers, Theses, and Dissertations, Eighth Edition: Chicago Style for Students and Researchers. (Affectionately shortened as 'Turabian'.) The book itself is a greatly condensed version of the monolithic Chicago Manual of Style (CMoS). Note that while 'Chicago' style citations are standard for most humanities and social sciences, some disciplines (mostly scientific) use other style guides like APA or MLA. All this is covered in Turabian.