rules_invoke_component() - Getting the value of the Provided Variable
From the "Tiny book of Rules":

Invoking components programmatically 

Rules components are handy tools for allowing site builders to customize their own actions and 
conditions. If you are writing a module that allows site builders to set custom conditions (or 
actions), you can let them set these up as Rules components and then evaluate selected components 
programmatically. This works in a way analogous to invoking events, by using 
rules _invoke_component() . 

The first argument is the (machine) name of the component, and any subsequent arguments are 
variables sent to the component. 

// Included somewhere in your custom module. 

$component name = $settings [' rules component name']; 

// Any variables provided from the component are returned from its evaluation. 

$result = rules _invoke_component ( $component_name, $var 1, $var 2 ) ; 


So the last 2 lines in the quote above should answer your question.