I like
Cassia a lot too. I'm also a fan of
Cassandra although at the end of the day, the 'dra' of
Cassandra feels really heavy to me so I'm not sure I could ever use it.
Of your combos, I like
Cassia Rosalind the best.
Re: the other names, I like the sound of
Cassius but not the meaning and I'm not fond of
Cassidy as a fn at all.