Spoiler:
You're right, as Dion finds comfort when he sees Roxanne crys because it means she was still kinda human in a way. Dion always wanted to be free and protect the weak, however, him being born into this household says otherwise. But later when Roxanne kills the father Dion leaves (dont know where), as it was for his and Roxanna mental state. Dion was obsesses with Roxanne crying which gave him comfort, however, Roxanne really did want to help him but because he killed Asil she couldn't mentally. He does come back for a bit to tease her. While this is going on Jeremy is their old household trying to fix the family, so one day Roxanne can come back (Jeremy do be sweet sometimes). Roxanne is currently with at Cassius's household where she is getting treated. Cassius's sister (original fl) really likes Roxanne and wants her to marry her older brother to become part of their family (the sister is so cute). And the original Male leads are gonna also find interests/like Roxanne.
Very sad spoiler
Asil ripped body pieces were used by Dion's mother Maria to make a doll called Nyx. Later Roxanne sees this doll and does break down, as her younger brother body was turn into that, however, Nyx does comfort Roxanne and tries his best to respect her.
Dion is just like his mother, as Maria is really obsess with Sierra, Roxanne's mother because she is really beautiful.
Cute spoiler:
Cassius purifies Roxanne so the poisonous butterflies won't eat her whole. Roxanne later wakes up and realizes she's in Cassius household and he comes down and tell her that she's his prisoner now ε=ε=(ノ≧∇≦)ノ
Dion and Roxana. They are both much similar people. Both of them were brought up in an environment where being strong was the only way and their fathers words are the law. That’s why he couldn’t deny his father when he killed Asil. Maybe he didn’t even feel anything as he had this deeply rooted ideals that weak have no place here. She understands why he did it but that doesn’t mean she accepts it. She understands it thats why she is disgusted at herself.
I think it was the raw moment of emotion from Roxane that made him so obsessed with her. Like he saw something unique n new in his jaded life that only he had access to.