How to call a secured route using AWS Lambda?

This is the "code" section of my AWS Lambda function. It works fine when I use this on our staging environment (non-SSL.)

I've tried to use the answer from this stackoverflow post, but I am receiving an npm error Cannot find package ssl-root-cas, and I'm not entirely sure if I'm able to install node packages.

'use strict';

const https = require('https');

var rootCas = require('ssl-root-cas').create();

https.globalAgent.options.ca = rootCas;

/**
 * Pass the data to send as `event.data`, and the request options as
 * `event.options`. For more information see the HTTPS module documentation
 * at https://nodejs.org/api/https.html.
 *
 * Will succeed with the response body.
 */
exports.handler = (event, context, callback) => {

    var url = 'https://admin.domain.com/api/schedule/checkForPublishedScreeners?authentication_token=mytoken';
    https.get(url, (res) => {

        let body = '';
        console.log('Status:', res.statusCode);
        console.log('Headers:', JSON.stringify(res.headers));
        res.setEncoding('utf8');
        res.on('data', (chunk) => body += chunk);
        res.on('end', () => {
            console.log('Successfully processed HTTPS response');
            // If we know it's JSON, parse it
            if (res.headers['content-type'] === 'application/json') {
                body = JSON.parse(body);
            }
            callback(null, body);
        });

    }).on('error', (e) => {
        console.error(e);
    });
};

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