Yes, you can. The Servebolt Cloud supports NPM or Node.js on your Bolts for build processes and such.
It is, however, not possible to use Node.js as a webserver because the primary engine behind our webserver setup is PHP. In addition setting up your own webserver without some type port forwarding is not possible without administrative rights. And lastly, running your application behind a webserver we won't have control over is unpredictable at best as we can't ensure either your or our own safety, plus you would miss out on our blazingly fast setup.
An example would be trying to use Strapi headless CMS with us. It starts up its own Node.js server and sets up access to a not well-known port of 1337 as default. We don't allow access to our servers via that port and therefore running such an application with us won't be possible. Changing the port to a well known port like 443 for HTTPS will not work either. Only privileged software is allowed to be accessed with ports under 1024.