[kenshiromusou]

Friends,
I guess native speakers don't like romanization a lot, but I would like to know if japanese interjections obey modified Hepburn (revised Hepburn - second variant).
I never used it on interjections coz I don't know the source of them.
Could you give me an accurate explanation about the theme?
そうさ夢だけは...
Is there any syllabic division in this "sousa" (interjection "Yes, that's right"...)?
"Sou-sa"? "so-u-sa"?
I have the sensation the pronounce is "sou - sa" [sôsa?]
Or the correct is Don't use romanization with japanese words no-derived from kanjis?

Thank you very much.
If here isn't the right place, please move the thread.