Question: I wanted to highlight a particular chord of my [previous question](https://music.stackexchange.com/q/114106/77758) because it was bugging me a bit. What would you call a dominant triad over a subdominant bass, in pop/jazz roman numeral analysis? It could be seen as a `V7` in third inversion, but if you have a strong subdominant bass it doesn't really sound like it. But just calling it a `IV` seems... meh. Especially because we call the inverse, a subdominant triad over a dominant bass, a sus chord.

**Update**: Thanks all for your responses. As most of you have said, roman numeral analysis isn’t really suited for these kinds of chords. I might decide to just slash chords for bass and then come up with a different way to notate secondary chords and modulations in a functional manner. I don’t want to do this literally because that doesn’t make sense in a tonic-agnostic notation.

[![Sample](https://i.stack.imgur.com/MbtNF.png)](https://i.stack.imgur.com/MbtNF.png)

Answer: 
I see two ways to analyze this. First, it's just a IV-V7-IV with a subdominant pedal. Another possibility is a IV-V42-IV progression. Both give the same note. I think the first describes the music a bit better. It might be worth looking at some of Handel's stuff as he liked the third inversion seventh enough that it's been commented on in the music history books.

"Passing" or "non-functional" chords are not always easy to describe; they often arise from just voice-leading considerations rather than being part of a harmonic direction. (They don't conflict with harmonic functions, they only "decorate" them.)
Normally the melody do-ti-la above IV (the subdominant) will be considered (the middle not e) as passing tone. Now together with parallels of 3rd and 6th we get a resoti (V) chord. I think it is most useful to consider this passage as a slash chord and it will help you to transpose it easily in other keys.

I think the idea of passing tones or suspensions 6-5;9-8;11-10 is more logical than the 3rd inversion of V7.