Indeed it's much older:

"The poem is recorded in its fullest form in the Vercelli Book, a late-tenth-century West Saxon manuscript which was left in Northern Italy in Anglo-Saxon times. Vercelli is on the road to Rome; the manuscript was either abandoned or forgotten by a pious Anglo-Saxon pilgrim. An Old Northumbrian version of part of the poem also appears, carved in runic script, on the late-seventh-/early-eighth-century"

Source: https://www.arts.gla.ac.uk/stella/readings/OE/ROOD.HTM

It’s Anglo Saxon, which much older. With a bit of effort a modern speaker can read Chaucer which is about 1300

I'm suggesting it's 1) English and 2) more than 400 years old.