I haven't read any but the briefest of summaries on the "Song of Roland", so I'll withhold comment on that. However I did spend some time in European history (long ago, and not much, so take it with a grain of salt) so I'll comment on stuff happening at about that time.
: They weren't really invaders. The French (ie Charlemagne, Roland et al) were
: invading Spain, and the Muslims were fighting for the Spanish.
Mmm, not quite. The Muslims were, uh, "uninvited," shall we say. Charles the First was invading Moorish Spain, yes, but IIRC mainly to secure the passes through the Pyrennes Mountains after a failed Moorish invasion of France the previous year.
That the Moors were probably better stewards of Spanish lands doesn't erase the fact that they were conquerors.
: The
: Saracens were basically portrayed as sub-human infidels, but what would
: you expect from something written in 12th Century France?
Yeah. The West at that time was a pretty nasty place, and xenophobia wasn't the least of the problems. Neither was their religious intolerance.
-- Steve's thinking of digging deeper into that time period... plenty of interesting material for stories back then. Or so Guy Gavriel Kay (The Lions of Al'Rassan) thought.