Ryoochan is the only 13th generation girl whose name really stuck, other than the now-graduated Kaoru. I can't help but wonder if I would have noticed had she and Yuko didn't have their last names in common, but they are indeed similar in quite a few regards. First of all, midget height (Ryoochan is shorter than Takamina, according to her profile!) and yaeba teeth. In addition, Ryoka's hairstyle in her 2012 profile picture reminded me of Yuko's GIVE ME FIVE! look on the CD covers.
Aside from her appearance, if the few things I know about her are enough to judge from, Ryoochan is very lively and energetic. She even wants to be an drama actress in the future! Also I recently read that when the new Team A performed for the first time, Mariko-sama asked the members to do a famous perverse gag onstage that is considered embarrassing for idols. Ryoochan was only one of the two girls who did well. I think this speaks volumes about her personality, aside from the cute look she has in pictures.
Another moment in her theater performances that I can recall is Ryoka trolling Umechan. Umeda asked who her Team K oshimen was, and Ryoochan slowly turned towards her.... Only to say that her oshi is Yuko.
Speaking of her onstage performances, I really wish that Ryoochan had been promoted to Team K instead of A. The two Oshima's would have made a kickass duo: The AKB center + One of first RS promoted from the 13th generation, and hopefully a future ace.