Kinda a trick question. Yes it is a Roadster since it's a sports car and new by not having anything to do with the Lotus derived platform. And since it uses the "skateboard" from under the Model S and Model X, one might say that it is a performance version of the model S. Though from the description I don't think much of the actual Model S bodywork would apply.
I guess in my head I always pictured it as its own model and not just a Model S variant (like a wagon or convertible would be). Though, I guess the Model X is technically its own model and it will still have Model S underpinnings.
I've got to start getting in the habit of thinking of the skateboard as a platform and not necessarily a "model"