rollup.config.js

import babel from '@rollup/plugin-babel';
import postcss from 'rollup-plugin-postcss';
import flexbugs from 'postcss-flexbugs-fixes';
import postcssPresetEnv from 'postcss-preset-env';
import { terser } from 'rollup-plugin-terser';

const addPlugins = () => {
    return [
        postcss({
            extract: true,
            minimize: true,
            use: ['sass'],
            plugins: [flexbugs(), postcssPresetEnv()],
        }),
    ];
};
// rollup.config.js
export default [
    {
        input: './src/sass/main.scss',
        output: {
            name: 'MainStyles',
            file: './build/styles.min.css',
            format: 'es',
        },
        plugins: addPlugins(),
    },
    {
        input: './src/scripts/index.js',
        output: {
            file: './build/index.min.js',
            name: 'MainScript',
            format: 'iife',
        },
        plugins: [babel({ babelHelpers: 'bundled' }), terser()],
    },
];