Load user by specific role

One possible way is by using the role__not_in parameter like so which excludes all other roles except subscriber:

// Include only the following role(s):
$roles_in = array( 'subscriber' );

$roles_not_in = array_diff(
    array_keys( wp_roles()->get_names() ),
    $roles_in
);

$args = array(
    'role__not_in' => $roles_not_in,
);

$subscribers = get_users( $args );

But of course, if you know the exact roles that should be excluded, then just do 'role__not_in' => array( 'role', 'role2', 'etc' ).