I did find a bit of broadcast video of Oswald speaking with press that was published by CNN. He says charged, sir, protested and representation with what appears to be very little trouble. I have no experience with analysis of speaking so I will say no further about the way in which he pronounces words. https://m.youtube.com/watch?v=jY8fRTLtgzA

I feel like this is an atypical type of answer so I'll take it down if the mods say it breaks the rules.

The actor who plays Oswald, Daniel Webber, is from the city of Gosford, New South Wales, Australia. My wife tells me that non-rhotic accents (accents in which the "r" gets dropped if there's a vowel before it but not after it) are common in Australian English. She thinks that the accent in question is all the actor, not the character he portrays. She also listened to a radio broadcast of Oswald because she had the same question and she said she couldn't hear any trace of a non-rhotic accent in Oswald's speech.