Ceridwen - This is by far my favorite with Rosalind and if we assume you get pregnant again when Roo is about 10-11 months old (fingers crossed) then she'd be that beautiful winter-fairy you mentioned a few months ago. Ceridwen Ophelia Alcyon though I'm sure your BF/FI would prefer a "normal" name in there so Ceridwen Fiammetta Isobel or Cerdiwen Elvira Alcyon. (Does Elvira count as "normal"?)
Zenobia - Second choice. Roo and a summer Zenobia would be brilliant. Zenobia Atlanta Matilda (I know your friend already has one but does that mean it's out as a mn?) or Zenobia Natasha Ophelia would be beautiful.
Fiammetta - I still love this and think it's stunning but is it too frilly in comparison to Rosalind? (Does it make Rosalind feel less girly?) I think this could make a brilliant mn to counter Illyria.
9 months? Whew... you have more lady cojones than me. Rowan is 18 months and some days I think this summer might be too early to start TTC... she is going through a "throws a tantrum over everything" phase and it's wearing me out.
I definitely like Fiammetta the best from your list, followed by Zenobia.
May I just say that I love your daughters name and all of your contributions to nameberry.
From your list, I love Fiammetta the most.
What about Melusine/Melusina, the french version of Melisande? There's a Luxembourgish fairytale surrounding Melusine in which she's half human and half serpent and marries a king. She curses a city and... I think it'd be better if you looked it up. I'm bad at explaining it. Melusine, unbenownst to almost all, is the starbucks insignia. The imagery I think of when I hear Melusine is stunning.
Melisande may also be slightly too close because of the shared nd ending/3 syllables with Rosalind.
Alys (traditional version of Alice; perhaps as a middle)
Loveday (given to boys and girls in the past born on loveday)
Melusine Iris Violetta