Translated page here has two tunes (culled from elsewhere on the Internet, I'm pretty sure I've seen them in other places by now). Obviously related tunes with a few melodic variations, and a pretty big metrical difference! (4/4 time vs. 3/8 time.)
What I really want is Semb's book. In the meanwhile, "Traditional Music in the Faroe Islands" gives a lot of examples in 3/8, 6/8, and even 9/8 time, which inclines me that way. (Since the tune is Faroese. According to that book there, Danish ballads are popular in the islands. Maybe the tune Semb uses was a tune for a Faroese version of the Roland ballad? That would be nice.
I'm not so great at relating ear-things to note-things, but I think Trio Medieval's rendition is the first one. Definitely the musical figure with "Ronsarvol" matches that one... yeah, the opening line has the two eighth notes. So does Glittertind's. So that's the tune I like.
Welllll... seeing as how neither tune is period, and they're clearly related, I don't think it's a great sin to use the tune I like better. I suspect the 3/8 version might be older, but I've got no reason to think it preserves any sort of authentic characteristic of medieval song, either. Although maybe I should read the book on Faroese traditional music.
Wait, wait, wait... one's in Phrygian mode and one's in Dorian? Huh, that's... odd. And interesting.