Answer:
The characters that made sacrifices in this poem are:
Bess: The protagonist's girlfriend who was tied up by british soldiers and when she hears the highwayman's horse, she fires the gun, and gives her life to warn him about the ambush.
The highwayman: He gets mowed down by the soldiers in the middle of the road, and dies in a pool of blood.
Tim the ostler: He loves Bess, but she's already got a man.