Should `wp_login` be used since it’s deprecated?

No, you shouldn’t, it’s deprecated

I don’t think wp_signon() can fill my needs in the same way wp_login() can

It does the exact same thing, but with a few new features

I read this runs after the login of a user and contains 2 parameter of which one is the username. With the username I can figure out their role.

You still need that username to call wp_login in the first place, the primary difference with wp_signon is that it’s passed inside a credentials array, rather than directly as a parameter.

If you had referred to the documentation, you’d have found a simple example taken from the codex:

$creds = array(
    'user_login'    => 'example',
    'user_password' => 'plaintextpw',
    'remember'      => true
);

$user = wp_signon( $creds, false );

if ( is_wp_error( $user ) ) {
    echo $user->get_error_message();
}

Also note:

Note: wp_signon() doesn’t handle setting the current user. This means that if the function is called before the ‘init’ hook is fired, is_user_logged_in() will evaluate as false until that point. If is_user_logged_in() is needed in conjunction with wp_signon(), wp_set_current_user() should be called explicitly.

A confusing point about your question

The question remains, should I use the wp_login() hook?

wp_login() is not a hook, it’s an actual function, and it’s the function that is deprecated. The hook is not deprecated, and muddling the two is confusing

Your Actual Question, and The One You Should Have Asked

I have a script that I’d like to run when somebody logs in, how do I do this and how do I get the users role?

By specifically asking about your attempted solution, you’ve constrained and limited the number of answers you could have gotten.

For example, wp_signon is called by wp_login, and the wp_login hook is triggered by wp_signon too:

add_action( 'wp_login', function( $username, \WP_User $user) {
    // the user object has all the information you need, the username is probably not that useful. Anything you do via the username will just fetch the `$user` that you've just been given
}, 10, 2 );

Reading the documentation here:

https://developer.wordpress.org/reference/hooks/wp_login/

We see the following:

Used By #Used By
wp-includes/user.php: wp_signon()