Rovhu's Pilot served the Peacekeepers when Rovhu was still controlled by them. Rovhu was a prison ship for the mentally insane, and at one time she carried only one prisoner - the insane Karvok.
We'll probably never know how, but Rovhu was eventually found by Crichton, Chiana, D'Argo and Jool, floating dead in space, still wearing her control collar. All the Peacekeeper crew had been turned into mindless zombies who were eating her Pilot, allowing him to regenerate before feasting on him. Karvok was also on the loose.
Rovhu's Pilot had been partially cut free from Rovhu so he had no control. Karvok had somehow patched himself in using a remote link-up. Not that it would have made much good, but the Pilot didn't even have enough arms to operate the console well.
Rovhu's Pilot's life came to an end when Karvok discovered that Crichton was seeking to patch him back into Rovhu, and as such get rid of Karvok. Karvok killed him by shooting a spear-like thing into his head.