I’d never considered that, but it’s actually quite a cute name! I’d probably pronounce it just like rose-elaine, so I believe that’s a long o, and I definitely do prefer Elaine to Ellen—no shade, I just think Elaine sounds a bit more elegant :D
For an invented Rose name, hmm… perhaps Rosemma, Roseia, or Roselouise haha XD
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Aspiring writer—I like odd names too much (◡‿◡✿)