@jyothsnamu

Make sure you are sym linking to vendor/simplesamlphp/simplesamlphp/public instead of vendor/simplesamlphp/simplesamlphp

Hey,
Is there anything else than adding monolor.services.yml to container-yamls array in settings.php?

I was able to achieve this by following

$group_content = $membership->getGroupContent();

$existing_group_roles = $group_content->get('group_roles')->getValue();

foreach ($selected_roles as $selected_role) {
$existing_group_roles[] = ['target_id' => $selected_role];
}

$group_content->get('group_roles')->setValue($existing_group_roles);

// Save updated entity
$group_content->save();