Roosevelt's position as an Imperialist is well documented. Roosevelt wanted a big Army and Navy and felt that America, as a natural course, should expand beyond the natural borders. Here is the evidence:
China: China had long been dominated and controlled by Europeans. Each country established spheres of influence, essentially a zone that was ruled by a European country. The US did not have any spheres in China but desired the ability to trade with those nations. Secretary of State John Hay established the open door policy that allowed the US trading rights in China.
Panama: The French had been building a canal in Panama for about 10 years but failed and abandoned the project. Roosevelt felt the US could finish the task. In 1901, he added the "Roosevelt Corollary" to the Monroe Doctrine which stated it was the US's right to intervene in Latin American countries to stabilize those nations. Panama was one such country. Roosevelt took the canal without the approval on Congress - very controversial.
Dollar Diplomacy is just as it sounds - expansion of dollars. In this policy, developed by President Taft, the United States desires to expand their economic position worldwide. Where Roosevelt wanted to expand the US military capabilities, Taft wanted to expand the US economic capabilities. This policy centered around the idea of expansion of wealth.
The former Spanish colonies in South America were struggling to establish a stable government and a stable economy. Taft believed, with the back-up of the Roosevelt Corollary" to the Monroe Doctrine, that the US served as the "big brother" to Latin American countries and in that role, the US should be the leader in the region. Therefore, it is the responsibility of the US to protect the interests of Latin America and their economies.