The first characteristic of an epic poem, the hero, has to be Roland. He's known for his bravery, volunteering for the most dangerous assignments.
Charlemagne would represent the second characteristic. He's the leader of the Frankish (French) forces. His purpose in the epic is to fight to regain lands lost to the "infidel", non-Christians.
Gabriel would represent the third characteristic. He is god's emissary and leader of the angels that help the French army. He also leads Roland's soul to Paradise after his death.