Chords can be analyzed with roman numerals to indicate function:
C, Am, Dm, G
I, vi, ii, V (or
I, VI-, II-, V in jazz theory)
And inversions may be analyzed by adding an arabic numeral indicating the note which takes the lowest voice:
C/G, Am, Dm, G/B
I/5, vi, ii, V/3
But what about polychords, and their ambiguous cousin, slash chords?
C, Am, Dm, F/G
I, vi, ii, IV/2
The "/2" seems a bit unclear. You could write "IV/V", but that's also a secondary dominant.