rollup.js : How to execute a given module, and returns the result of the execution at build-time?

How to specify rollup.js to execute a given module, and return the result of the execution at build-time ?

Webpack have the val-loader

  {
    test: require.resolve("src/createConfig.js"),
    use: [
      {
        loader: "val-loader",
        options: {params: "my params"},
      },
    ],
  },

E.g. I have the function in createConfig.js:

export function createConfig(params) {
  var config = {}
  // dynamically build config from static params, quite verbose code (browse plugins array) 
  return config;
};

Then in main.js

 import createConfig from "createConfig.js";
 console.log(createConfig); // this shows not a function but object