Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Somber, Reverent
Given that thousands of Franks die, not to mention hundreds of thousands of Saracens, you'd hardly expect Roland to be a cheery ride. Funny one-liners? Knock-Knock jokes? Moments of innocent physical comedy such as slipping on banana peels? Not a chance. Bananas weren't even invented then. (jk, Dole just wasn't exporting to Carolingian Europe yet). Who's making jokes now, eh? Not this poet, that's who.
He keeps a straight face throughout, describing Frankish exploits with awe, triumph, and tenderness and Saracen exploits with anger and moral superiority. When we first meet Charlemagne, for instance, the poet is all respect, pointing out his age and experience but still great-lookin' bod:
There sits the King, who rules fair France.
His beard is white and his head is hoary,
His body is well proportioned and his look is fierce:
Anyone seeking him needs no one to point him out. (8.116-19)
Since God's the guy who made Charlemagne great, the poet keeps things reverent.
Plus, his tendency to tell us what's going down before we have a chance to see it happen gives a kind of gloom-and-doom feeling to the action. There's a great example in the 12th stanza, when the poet's describing the various peers summoned to advise Charlemagne and everything sounds normal until he adds this dark note of foreshadowing:
Now begins the council that went wrong. (12.179)
See how that casts a bleak mist on things? Chock-full of these zingers, the Song of Roland can't help being a somber ride.