Alright, let's get Firebase into your project! First, you need to install the SDK. You can do this by running either npm install --save firebase or yarn add firebase. Once that's done, you'll need to initialize Firebase in your project using the configuration settings from your Firebase project.

Firebase makes it super easy to handle authentication. You can use Email and Password, Google, Facebook, and more. To set up email and password authentication, head over to the Firebase Console, find the Auth section, and enable Email/Password authentication. Simple, right?

Now, Firebase Authentication doesn't come with built-in roles. But don't worry, you can create custom roles using Firebase Cloud Functions and Firestore. Start by creating a Firestore Database in your Firebase project. Then, set up a Cloud Function that listens for new users, assigns them a default role, and saves this info in Firestore.

To get Firestore up and running, go to the Database section in the Firebase console and create a Firestore Database. Next, install Firebase Cloud Functions with npm install -g firebase-tools. Initialize Cloud Functions in your project by running firebase init functions.

In your Firebase Cloud Functions folder, write a function that assigns a default role to new users. This function will listen for new user registrations and automatically assign a "user" role.

Deploy your Cloud Functions using firebase deploy --only functions. Once deployed, this function will automatically assign a user role to any new user who signs up. Pretty neat, huh?

In your app, set up role-based access control using Firebase Authentication and Firestore. Fetch the user role from Firestore and use it to decide what to render and what not to, based on the user role.

To change user roles, create a separate function in Cloud Functions. This function will take the user's email and role as input and update the role. Make sure only admin users can execute this function for security reasons.