Yes, they knew he was Roxas. Wasn't he so cute and polite? Awww.
And then Sora came in, and the maids saw how similar they were. They had the same sweet face and blue eyes. Their hair was the most different thing about them, and the colors they wore.
The maids backed off so that the brothers could talk and catch up. They hadn't seen each other in awhile, afterall.