AAA & Roman numerals

So here's a question (with apologies if it's been addressed previously
in the archives) about abbreviations and language.

Would you consider it necessary for AAA-level compliance to mark up
Roman numerals, and if so, how would you do it? My thought would be
something like:

...its fifth international disability advocacy conference, Shared World
<span lang="la" title="5">V</span>.

Is there preferred markup for Roman numerals?

Thanks.

Colin Lieberman
IT Manager
Disability Rights Advocates
449 15th Street, Suite 303
Oakland California  94612