So I finally got around to listening to Trio Mediaeval's "Folk Songs" recording. I bought it at the used CD place a while ago; it's Norweigian folk songs sung in the Trio's ethereal style. It contains "Rolandskvadet," listed as "medieval ballad," and it's a Norweigian version of the Roland story.
Looking here about deflates any thought that this is, in fact, a medieval ballad preserved with music. There was a "saga of Charlemagne" that includes a version of Roland, but that would be prose. So, not this. I'd guess it sits about where the Robin Hood ballads collected by Child sit - the source material is definitely period, and the musical style is antique, but you can't actually authenticate it past the 1800s.
Still, I'm going to throw it on the translation pile. It's Trad, but it's Trad with clear medieval roots and a flattish melody that fits with what I've been reading about oral epics. It's at least as neo-medieval as anything I'd compose myself.
Edited to add: A random translation of the Glittertind lyrics, of which there seem to be more than the Trio's liner notes.