Roman numerals can be used for aspects of instrumental notation, which are for performance, rather than analytical purposes. For instance, Roman numerals are used to denote: positions in classical guitar music (for instance, see this post); which string a note or passage is to be played on in bowed string music.
The wikipedia page about Roman Numerals gives examples of both analytical and performance markings:
In music theory, the diatonic functions are identified using Roman numerals. (See: Roman numeral analysis)
In musical performance practice, individual strings of stringed instruments, such as the violin, are often denoted by Roman numerals, with higher numbers denoting lower strings.
However, inversions (I think this is what you mean by voicings) of chords are shown using either letters or numbers (in figured bass), as an addition to either a Roman numeral or bass note. For example, a first inversion of chord I can be shown as Ia or I6.