Let's not forget that STXI took place some years before Kirk Prime made contact with Romulans in the other timeline... Yet the nuFederation already knew what Romulans look like, had knowledge of Romulan dialects, and appeared to be in a dialogue with the Romulan government and capable of complaining to them about Nero.
The situation vis-á-vis UFP and RSE is probably rather different in the two universes, then. Might very well be something that happened after 2233, as per the premise of the reboot.
In the New timeline the first visual contact with the Romulans would have been Ayel's mug on the Kelvin's viewscreen. Audio first contact, (for humans) would have taken place during the NX-01's mission in both timelines. Since the treaty that ended the Romulan War was negotiated over subspace radio, I imagine humans (and their allies) have a good knowledge of Romulan dialects in both universes.
I imagine the UFP didn't find out the attackers were Romulan until the Kelvin's logs were reviewed and the survivors questioned. They probably had a few questions for the Vulcans after that.