The former hospital chief executive at the center of a bribery conspiracy that ensnared former State Senator Carl Kruger and others was sentenced on Monday to three years in prison. The former executive, David P. Rosen, 64, had been convicted of bribing Mr. Kruger and two other legislators in return for having them use their influence in Albany to benefit his healthcare organization, MediSys, a nonprofit sponsor of hospitals and nursing homes in Brooklyn and Queens. The conspiracy, which also involved a lobbyist, another hospital executive and a healthcare consultant, has been seen as casting light on the pervasiveness of corruption in Albany and on the often-cozy ties there between legislators and hospitals.