One of the problems with getting a lot of your history from fantasy novels is that it's easy to conflate things with similar names.
I just finally worked out that these things are not directly related to each other:
- The Song of Roland, an 11th-century epic poem that fictionalized a battle of Charlemagne's army in 778. (You can read the whole poem online in English if you're so inclined, all 291 verses of it.)
- Childe Roland to the Dark Tower Came, a poem by Robert Browning, the protagonist of which may be the same Roland but the connection is unclear. (This poem is also available online, and is much shorter than the Song of Roland. And this one was at least part of the inspiration for various other works.)
- Childe Harold's Pilgrimage, a poem by Byron that has nothing to do with either of the above. (You can read this poem online too, of course. It's got well over 400 verses.)
- The Child Ballads, a set of folk ballads collected by Francis James Child in the late 1800s; they have nothing at all do with any of the above.