Which ruler restored the territories taken from Rome by Orodes II?

Phraates IV, the ruler of the Parthian Empire, is credited with restoring the territories that had been taken from Rome by Orodes II. Orodes II had previously engaged in conflicts with Roman generals, leading to territorial gains for the Parthians. However, Phraates IV's reign saw a shift in power dynamics. He negotiated peace and territorial boundaries through both warfare and diplomacy. His consolidation of power and subsequent military campaigns allowed him to reclaim and stabilize the regions that had changed hands.

This context is crucial in understanding why Phraates IV is the correct answer. During his rule, he managed to reassert Parthian influence in the region and maintain control over territories that were once part of the ancient Roman Empire, thereby reinforcing the power of the Parthian state.