Allan-a-dale is a minstrel (a.k.a. traveling musician) who hangs around with Robin Hood's band of merry men. He's not only a musician; he's also an outlaw, a fighter, and a troublemaker. Allan-a-dale and Friar Tuck are good friends. We see them at Rebecca's trial by combat arguing good-naturedly about whether Athelstane of Coningsburgh rose from the dead or not at the Priory of Saint Botolph.
The miller is another one of the guys in Robin Hood's legendary little band of merry men. In Ivanhoe, he mainly appears to duel with Gurth during Gurth's first meeting with the guys in the forest. Gurth is carrying Rebecca's money back to Ivanhoe at Ashby-de-la-Zouche when the outlaws find him. Robin Hood is inclined to let Gurth go, since he's serving the Disinherited Knight, who kicked serious Norman butt at the tournament that morning. The miller wants that cash, though – they are thieves, after all.
The outlaws agree to settle matters with a duel between Gurth and the miller, fought with staffs. As they battle, the miller loses his temper and his focus and Gurth smacks him on the head with his staff. The thieves all shout, "Well and yeomanly done! [...] fair play and Old England for ever!" (11.52). Apparently, for the outlaws, there's nothing more bonding than watching one of their buddies get knocked out by a strange pig-herder. Still, without this first triumphant encounter between Gurth, the miller, and the outlaws of the forest, maybe Gurth would not have been able to convince Robin Hood to help him rescue Cedric from Torquilstone. All's well that ends well, we suppose.
An outlaw of Sherwood, Scathlock blows a trumpet on Robin Hood's orders to show Prior Aymer how real Englishmen play.