"I was so nervous doing the red carpet that I basically skipped everybody because I was worried, I kept spontaneously crying, I feel like I'm probably gonna do it now," she explained, before tearing up.
Rose was concerned that when reporters asked what she had planned next she'd accidentally blurt out Batwoman "or just start crying and they'll think, 'She doesn't look so good.' But I'm so thrilled."
So, what's the story behind all the waterworks?
"I feel like the reason I kept getting so emotional, growing up watching TV I never saw somebody on TV that I could identify with, let alone a superhero," said the queer star. "I've always had this saying, well not me, Oscar Wilde, which is be yourself because everyone else is taken. The second motto when I came into this industry is be the person you needed when you were younger and I feel like one motto led me to the other and I kept crying about it."
She explained that she's excited to see people dress up as one of her characters without slipping into a prison jumpsuit anymore -- a nod to "Orange Is the New Black" -- and is thrilled to be able to visit children in hospitals in costume as the superhero.
The 32-year-old stunner said the show actually won't be her first time sporting bat wings.
"We grew up with not a lot of money, so I would make my toys and I would make bat wings out of recycled cardboard boxes and I would sleep in them and run around in them and jump off high things," she told Fallon. "[My mom] said we would have to keep gaffer taping them ... and I just lived in them. And now I'll get ones that aren't made of cardboard."
Rose will make her debut as Gotham's red-headed savior during The CW's annual crossover event this winter, before hopefully getting a show of her own in 2019.