If there will be an asexual romance then probably for a exotic race like dragonborn to avoid complains accusations of bestiality.
I mean.... If you have speak with animals up (which is magic that affects you, and not the creature you're interacting with, so you can't say they are influenced), then even Scratch passes the Harkness test... And doesn't spend a large portion of his energy acting superior towards you in one way or another.
*Ahem*
While I support the existence of dialogue lines to indicate your feelings on the matter as a potentially asexual, but not aromantic, character... the dialogue would need to be more than a throw away line - it would need to be a multi-line discussion, if we're being mature about this; characters may be fine with having a romantic but non-sexual relationship with your character, but given that some of them at least are already backstory or overt characterisation defined as being sexual people in some sense, they are likely going to have needs/wants that don't match that. Perhaps your character is okay with them pursuing those needs outside of your relationship; perhaps they won't be and that will lead to a break down; perhaps your character is okay meeting those needs for their romantic partner, even if they don't have the drive for it, because they want to 'do that nice thing for the person they care about' (This isn't uncommon; I know a couple of ace people, and at least one of them is physically intimate with their partner moderately regularly, because it makes them happy to make their partner happy, even though they don't get anything other than that by-proxy enjoyment from it). As others have mentioned, it would make the most sense if different characters reacted differently to this (maybe you can eventually pursue a romantic but non-physically sexual relationship with Lae'zel, but her 'line' is that she's still going to take care of her needs with others, and you'll need to accept that approach to continue with her - maybe Gale, on the other hand, is open to keeping things non-phsyical but also exclusive with you, and that is the approach that he will accept, etc.).
Unfortunately, it's a complexity of relationship that, if it is done, really needs to be done carefully and well, or else it will come off worse and more distasteful than if they didn't do it at all.
