Rollup.js - combine multiple js files into one big file

Question

I have multiple files like this:

// File one
const A = CreateSomething();
export { A }; 

// File Two
import { A } from 'File One';
const other1 = A.injectSomething({ methodA: "a"}); 
export { other1 }; 

//File Three
import { A } from 'File One';
const other2 = A.injectSomething({ methodB: "b"}); 
export { other2 }; 

what I need is only one file in dist folder combining all this together. like so:

const A = CreateSomething();

const other1 = A.injectSomething({ methodA: "a"}); 
const other2 = A.injectSomething({ methodB: "b"}); 

export { A, other1, other2 }; 

how can I achieve this using Rollup?