One quick moment of clarification was that the Return of Godzilla was actually 1984, not 1985. When it was released in America, they changed the title for American audiences to Godzilla 1985. But it's true release was '84.
Anyway!
From what I can hear in the teaser, the roar itself is classic in style but very modern in terms of presentation. There is a bit more of a hiss to it, which is very reptilian, and also a bit more of a groaning sound at the end when it rolls off.
One other thing to note about the roar from the teaser was that it was a proof of concept piece put together by Gareth Edwards, and while he's great with digital effects the sound of the roar was, at least to me as one studying to be a sound engineer, unfinished. There are two to three tones sounding at once during the initial impact of the roar which I can make out, which gives it a rough and unrefined feel. As nice as it sounds, I think the final roar is going to sound a tiny bit different and a little more crisp than the one in the teaser.
Definitely still a good roar though. I'm very happy with where they've taken it so that it's still classic Godzilla but modern enough to fit the new image they're presenting.