It doesn‘t make much sense to analyze music like temporary film music that is not written in this spirit or context by Roman numbers. You can compare this minimal music with the chord material of early Renaissance music.
We even don‘t know actually the key. Has the key sign f# been set originally by the composer or by the editor? Compare the added sheet music!
„After a fixed process, Nyman chooses [...] very short verbatim quotes from the classic template and subjects them to a minimalist repetition. The tonal orientation is retained, but the harmonic progression is changed. Finally, whole bars of the source material are missing and the harmonic stages are abruptly juxtaposed, instead of logically following a cadence. " Michael Nymans Musik als Musikgeschichte von Volker Straebel, 1999
The result is music that has both charmed initiates and uneducated listeners of the same musical appeal because it plays intelligently with tradition but on the other hand never becomes atonal.
(The German wiki commentary is more extended than the English ...)
Edit: Well, if I had to analyze this piece with RN
I would first define whether it is in a minor, G major or e minor:
a minor => IV46
G major => bVII 46 (the flat sign notated below the RN
and then the other RN should be adjusted to the key and also the half note changes in the r.h. could be determined. But as I said: it doesn‘t make sense!