The main point of the Roosevelt Corollary was to declare that the United States had the right and even the duty to intervene in the affairs of other countries in the Americas.
The Roosevelt Corollary stated that the United States would be a good friend to any country that kept its affairs in order. It promised that these countries would have good relations with the US. However, it also essentially threatened any countries that did not keep their affairs in order. It said that the US would intervene in the affairs of any country that did not manage its affairs well.
Roosevelt Corollary basically asserted America's right to intervene in the affairs of Central America and the Caribbean. What it did was that it expanded America's role to be involved in Central America and Caribbean's. Roosevelt issued this to the Doctrine to forestall European intervention.