How can I insert checkbox in a form with Symfony

I'd like to insert a checkbox in my form with Symfony. I used CheckboxType in my UserType.php file for field "role". I would like to set the value "ROLE_ADMIN" for when the checkbox is checked. The value of a checkbox is a boolean and at the moment this is why I am stuck. I currently have this error message : Unable to transform value for property path "roles": Expected a Boolean. Which doesn't correspond with the value my database is asking (json type). I think I am missing a step and I don't know how I can move forward in the construction of my form.

How can I set my checkbox value so that "user" role value changes for "ROLE_ADMIN" (instead of "ROLE_USER") when checkbox is checked ?

Register.html.twig

{% extends 'base.html.twig' %}

{% block title %}Incris-toi !{% endblock %}

{% block main %}

<main>

    <header></header>

    {{form_start(userform)}}

        <div class="form container">
            <div class="form-floating mb-3">
                {{form_widget(userform.email, {'attr' : {'placeholder' : 'Mon adresse e-mail', 'class' : 'form-control'}})}}
                {{form_label(userform.email, 'Mon adresse e-mail', {'label_attr' : {'class' : 'label'}})}}
            </div>
            <div class="form-floating mb-3">
                {{form_widget(userform.password.first, {'attr' : {'placeholder' : 'Mon mot de passe', 'class' : 'form-control'}})}}
                {{form_label(userform.password.first, 'Mon mot de passe', {'label_attr' : {'class' : 'label'}})}}
            </div>
            <div class="form-floating">
                {{form_widget(userform.password.second, {'attr' : {'placeholder' : 'Confirmation de mon mot de passe', 'class' : 'form-control'}})}}
                {{form_label(userform.password.second, 'Confirmation de mon mot de passe', {'label_attr' : {'class' : 'label'}})}}
            </div>
            <div class="checkbox">
                <label class="remember-me-label">
                    {{form_widget(userform.roles)}}
                    <span class="checkmark"></span>
                    Je m'inscris uniquement en tant qu'organisateur.
                </label>
            </div>
            <button class="btn btn-lg btn-outline-primary mt-4 d-flex mx-auto">Je m'inscris</button>
        </div>

    {{form_end(userform)}}

</main>

{% endblock %}

UserType.php

<?php

namespace App\Form;

use App\Entity\User;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Form\Extension\Core\Type\SubmitType;
use Symfony\Component\Form\Extension\Core\Type\CheckboxType;
use Symfony\Component\Form\Extension\Core\Type\PasswordType;
use Symfony\Component\Form\Extension\Core\Type\RepeatedType;

class UserType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $builder
            ->add('gender')
            ->add('lastname')
            ->add('firstname')
            ->add('birthdate')
            ->add('occupation')
            ->add('nationality')
            ->add('nativelanguage')
            ->add('wishedlanguages')
            ->add('email')
            ->add('password', PasswordType::class, [
                'mapped' => false
            ])
            ->add('password', RepeatedType::class, [
                'type' => PasswordType::class,
                'invalid_message' => 'Les deux mots de passe doivent être identiques.',
                'options' => ['attr' => ['class' => 'password-field']],
                'required' => true,
                'first_options'  => ['label' => 'Password'],
                'second_options' => ['label' => 'Repeat Password'],
            ])
            ->add('roles', CheckboxType::class, [
                'label' => 'Role :',
                'required' => false,
            ])
            ->add('Subcription', SubmitType::class);
        ;
    }

    public function configureOptions(OptionsResolver $resolver): void
    {
        $resolver->setDefaults([
            'data_class' => User::class,
        ]);
    }
}

UserController.php

<?php

namespace App\Controller;

use App\Entity\User;
use App\Form\UserType;
use App\Repository\UserRepository;
use Doctrine\ORM\EntityManagerInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Annotation\Route;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\PasswordHasher\Hasher\UserPasswordHasherInterface;

class UserController extends AbstractController
{
#[Route('/register', name: 'register', methods: ['GET', 'POST'])]
    public function createUser(
        Request $request,
        EntityManagerInterface $entityManagerInterface,
        UserPasswordHasherInterface $userPasswordHasherInterface
    ){
        $user = new User();
        $userform = $this->createForm(UserType::class, $user);
        $userform->handleRequest($request);

        if ($userform->isSubmitted() && $userform->isValid()) {
            $user->setRoles(["ROLE_USER"]);

            $plainPassword = $userform->get('password')->getData();
            $hashedPassword = $userPasswordHasherInterface->hashPassword($user, $plainPassword);
            $user->setPassword($hashedPassword);

            $entityManagerInterface->persist($user);
            $entityManagerInterface->flush();

            return $this->redirectToRoute('home');
        }

        return $this->render('front/register.html.twig', [
            'userform' => $userform->createView()
        ]);
    }
}