It wasn't that Roman was a coward who didn't know how to face his problems, but he couldn't emotionally, and it had probably rubbed off on Bianca, who had been holding back so much. She still hadn't healed from the death of their parents, and Roman knew he had to confront the truth.
As for her having a descent of Asian in her looks, it wasn't a difficult one to guess. It wasn't that Roman was hiding it as a secret, but it was that she was young when their parents passed, so she wasn't able to hear it from them. And Roman never got a chance to say it; after they died, he drowned himself in taking care of her and making sure they were fine. As for why he hadn't mentioned it when things calmed down, it was that he had treated her like family ever since she was born, so he never thought about it again.
