You can get elites for either of your professions. Also, elites aren't the only skills you can capture; they are skills that you can only get by capturing them. I don't know if there are any skills that are not elite that you can't get from skill trainers or quests, though I doubt there are.
Look at it this way, if they add more elite skills for Elementalists and.. wait... Rogues aren't a class. I guess you mean Rangers? Anyway, if they add more elite skills for Elementalists and... your other class... you'll have your signets of capture already!
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