<select class="custom-select" name="roles">
    <option selected disabled>Choose a role</option>
    {% for role in siteinfo.roles if role.name != 'Admin' and role.name != 'Developer' %}
        <option name="role" value="1">{{role.name}}</option>
    {% endfor %}
</select>

private function adduser($context)
    {
        $now = $context->utcnow(); # make sure time is in UTC
        $fdt = $context->formdata();
        $u = R::dispense('user');
        $u->login = $fdt->mustpost('login');
        $u->email = $fdt->mustpost('email');
        $u->active = 1;
        $u->confirm = 1;
        $u->joined = $now;
        R::store($u);
        $u->setpw($fdt->mustpost('password'));
        if ($fdt->post('admin', 0) == 1)
        {
            $u->addrole('Site', 'Admin', '', $now);
        }
        if ($fdt->post('devel', 0) == 1)
        {
            $u->addrole('Site', 'Developer', '', $now);
        }
        if ($fdt->post('roles', 0) == 1)
        {
            $u->addrole('Site', 'Student', '', $now);
        }
        echo $u->getID();
    }