Never used OTP as connecting airport, but if like most then you will have to clear customs and passport control before your domestic connection as OTP being your point of entry into Ro.

If you go through baggage claim/customs you will no longer be air-side and need to go to the departures hall and back through security line etc. So you could visit the check-in desk and maybe get a lounge pass there.

I just do not recall seeing any signs for 'connecting flights' after deplaning at OTP.