There are three pieces of information present in a Roman numeral analysis of a chord.
- The root of the chord. (Shown by the Roman numeral, which refers to the scale degree of the root.)
- The quality of the chord. (Shown by the case of the Roman numeral, and possibly an additional symbol.)
- The bottom note of the chord, shown by the figured base number after the chord.
This is great, because we need to know these pieces of information! The root and quality of the chord are essential, and understanding that the bottom note of the chord can profoundly influence its function is vital.
But it’s necessarily reductive – it leaves out a lot of other information. To not leave that information out would be to fully notate music again.
In my experience, that reduction has a serious side effect for young composers. They seem unable to differentiate between chord voicing, as long as they adhere to the three pieces of information above.
This results in frequent awkward voicings – chords that on paper match the Roman numeral analysis, but don’t sound good. There’s more to a good voicing than to an accurate analysis. Balance, appropriate doubling, range-specific timbre, chordal character, and on and on. Until your understanding of chords goes well beyond the Roman numerals, you will fall into the trap of choosing ineffective voicings.