No roman-numeral harmonic-analysis representation exists in either Gradus data model (model gap)

Roman-numeral analysis attaches a harmonic label (e.g. V, ii°6, V7/V) below the bass staff at each harmony change, encoding scale-degree, chord quality via case, and inversion via arabic figures.

Gould briefly touches analytical markup; the fuller convention is drawn from standard harmony-pedagogy engraving (Aldwell and Schachter, Piston) rather than Gould/Read/Ross, which predate/underserve analytical notation as a print convention. Dorico's Roman Numeral Analysis feature is the closest industry-standard implementation.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.