Final answer:
The Nobel Peace Prize for helping to negotiate an end to the Russo-Japanese War was awarded to Theodore Roosevelt.
Step-by-step explanation:
The Nobel Peace Prize for helping to negotiate an end to the Russo-Japanese War was awarded to Theodore Roosevelt. He acted as a mediator between the two nations and played a significant role in bringing about peace. The peace treaty between Russia and Japan was signed in Portsmouth, New Hampshire in 1905, and Japan gained control over Korea and certain Russian bases in Manchuria.