After Eloquent query, you can modify rows by using map() function in Collections.

$users = User::where('role_id', 1)->get()->map(function (User $user) {
    $user->some_column = some_function($user);
    return $user;
});

However, this is not adviseable for bigger amount of data, cause you're downloading all the records into RAM and then doing the filtering. A better way is to perform such filtering on the database level, in the query.