Theodore Roosevelt: Nobel Peace Prize?

There have been over 100 Nobel peace prize winners since 1901. Today Obama won the price but I've been told he's not the first president to win the prize and that Theodore Roosevelt won the nobel prize a few years ago.
Why did Theodore Roosevelt won the prize when he was president of the United States? What did he do to win it?

Theodore Roosevelt won the nobel peace prize mostly because of the end of the Russo-Japanese War.
In 1901, President William McKinley was assassinated, and Roosevelt became president at 42. Roosevelt attempted to move the Republican Party in the direction of Progressivism, including trust busting and increased regulation of businesses. Roosevelt coined the phrase "Square Deal" to describe his domestic agenda, emphasizing that the average citizen would get a fair shake under his policies. As an outdoorsman, he promoted the conservation movement. On the world stage, Roosevelt policies were characterized by his comment, "Speak softly and carry a big stick". Roosevelt was the force behind the completion of the Panama Canal; he sent out the Great White Fleet to display American power, and he negotiated an end to the Russo-Japanese War, for which he won the Nobel Peace Prize.