So Dstahl tried to spin it that Romulans are a full faction, however they will either join the KDF or Federation at a certain point and will not have their own star bases, and will be "allies" and fight on their chosen side for pvp purposes.
The benefit for the Klingons is that the bulk of romluan players are either going to be ex feds, or people that don't have interest in the federation in the first place.
I beleive most will choose Klingon as their "Ally" and thus join the ranks of the KDF. This means that they will participate in KDF fleets and activites and things like the 20 man kdf starbase defense missions will actually have enough players to trigger, as well as pvp wait time diminishing.
Furthermore, it's inevitable that after being lumped in with us and listening to us lament all the things we don't have that we can find support for finally getting things like kit visuals, and unique stories to the KDF that expand on the war, the allied races liek Orions and Gorn, etc.
It's going to be a good thing long term as our Romulan Allies bring a mutual hatred of those do gooder onesie wearing upside down spoon flying weaklings!