User Role sample.

Role.php

<?php

class Role extends Model
{
    public function users()
    {
        // permissions まで含めると morphedByMany がよさそう
        return $this->belongsToMany(User::class);
    }
}

User.php

<?php

class User extends Authenticatable
{
    public function roles()
    {
        return $this->belongsToMany(Role::class);
    }
}