On what did the Roosevelt Corollary build?

The Monroe Doctrine

The corollary allowed that the United States should intervene in disputes between European and Latin American countries in order to legitimize European claims, consistent with Roosevelt’s characteristic “big stick” ideology.

The Monroe Doctrine had stated that any European efforts to colonize or interfere with American land would be met by intervention from the United States, so the Roosevelt Corollary saw the other side to the Doctrine.