Yup - just done a bit of googling and sure enough, Stephen King's hero is based on Rowland/Roland from (a) the poem by Browning and (b) the English folk ballad.
Nowt to do with the Chanson de Roland except for a reference to a horn that's blown and the name of the hero.
The folk tale is a good'un, though. As is Alan Garner's book.

Anne