I was dead tired when I wrote this I hope I didnt come off too abrasive. You are correct that the WRE faded away more than having an abrupt "Constantinople in 1453" end. I just really expected Romulus Agustulus, lol. I believe Odoacer kinda "ended" the chain of WRE emperors by deposing Augustulus and reigning as "King" under the nominal authority of ERE Emperor Zeno.
FInally, I found the game by searching "Rome".. :)