SecItemCopyMatching is not returning System Root certificates

I am using secItemCopyMatching API to find certificates in login, system and System root keychain, But it's not returning me System Root certificates. I am new to this, Could you please guide?

NSDictionary *query = @{
            (__bridge id)kSecClass: (__bridge id)kSecClassCertificate,
            (__bridge id)kSecAttrLabel: @"somelabel",
            (__bridge id)kSecMatchLimit: (__bridge id)kSecMatchLimitAll,
            (__bridge id)kSecReturnRef: @YES
        };

         CFArrayRef result = NULL;
        OSStatus status = SecItemCopyMatching((__bridge CFDictionaryRef)query, (CFTypeRef *)&result);