Lord Roke was a Gallivespian spy, working for Lord Asriel. He was the Leader of the Gallivespians who were working for Lord Asriel, and was on the commanding council. He flew on a blue hawk rather than one of the dragonflies that Lady Salmakia and Chevalier Tialys did.
In The Amber Spyglass Lord Roke followed Mrs. Coulter to the Church and assisted her in trying to save Lyra from the bomb that the Church was trying to use to kill Lyra. He killed Dr. Cooper, the scientist who had been at Bolvangar with Mrs. Coulter and had almost separated Lyra and Pantalaimon, and a witch who was serving the Church. When attacking the witch, just before the bomb was detonated, Lord Roke was killed. He died when the witch, killed by the last of the poison from his spur after he had thrust it into her neck, fell from the sky where she was flying on her cloud pine branch.
Lord Roke could use a lodestone resonator, a means of communication that is unique to the Gallivespians. Lord Roke used his lodestone resonator to communicate with the Chevalier Tialys while he and Lady Salmakia were spying in the Church, and later travelling with Lyra and Will.