I don't write Rogier as a total manslut to titillate and be horny on main. I write him that way for one, to be another way he's an opposite to darian, which is just a personal interest of mine lol. But for two, because hypersexuality as a trauma response for him simply made sense to me.
I saw his emotional detachment and general disinterest in bonding with others intimately, and thought 'that guy's got a void in him.' I saw his single minded obsession with his research, and thought 'that guy's gonna fill that void with everything but difficult self-reflection and confrontation of why that void exists to begin with'. It'd be a challenging thing to do even in our modern world of medication and therapy, so I can't imagine him sitting down with someone and talking it out. And he simply doesn't work that way to begin with. When he goes to sleep with Fia, he doesn't break down crying about his own problems. He cries over an unsolved conspiracy that he's obsessed with, because he's not going to puke up his feelings directly. He didn't seek her out for emotional intimacy and healing, because he is much more interested in denying he has much of an emotional state to begin with. Emotional detachment is not 'I feel a bit numb sometimes', or 'I have some angst issues and have trouble talking about my emotional state, but I'd be pleased to help you out with your emotional problems :)' It's alarm bells and dread going off when someone tries to get 'deep' with you. It's your heart rate spiking at the thought of someone confiding intimately in you. It's disgust with your own emotions, if you can even identify them to begin with. It's being asked how you feel and defaulting to a pleasant response and breaking down if someone acknowledges your horrible feelings for you because that is NOT normal. Normal for you is ignoring all of that icky, uncomfortable stuff. Normal for you is laughing nervously and hoping the conversation moves away from talk about everyone's feelings, because you have no idea how to handle that. So if someone is going to bury and deny the emotional, they're going to seek the comforts and outlets for feelings that would normally come from such intimacy via other means. They're poor substitutes, but they don't come with that anxiety over trying to grapple with something you simply do not and never have had the mental capacity to deal with. You get the dopamine hits and relief from stress using these purely physical indulgences. Good food, booze, casual sex, whatever works, because without it that void in you where intimate connections and healthy introspection should be yawns, and yawns, and yawns, until you're sure it's going to swallow you whole. Better fill it with something, or there's not going to be much of you left that isn't a miserable husk.