when talking about confirmed sexuality of homestuck characters or lack thereof, it is important to understand something: homestuck is, fundamentally, anti-label. homestuck, to use this as an example, is less concerned with confirming a character as a lesbian, and more with deconstructing what a “lesbian” or the idea of a lesbian is.

for example, look at the first in comic confirmed human gay character: dirk. he is, for all intents and purposes, what we would call gay: he confirms he‘s only interested in men, however when roxy calls him gay, he denies this label. he talks about how the label is a remnant of a dead civilization and, well, what does “sexuality” even mean anymore when there are only two people left on earth? what dirk is actively pointing out is that gay and straight and any other sexuality label exist in a cultural context, and can only exist in certain cultural contexts. this also retroactively applies to the beta kids: if your old civilization is dead, and you’re tasked with creating a new universe, why keep a system of sexuality which fundamentally exists on the basis of heteronormativity, i.e. having a “normal” and “the other”. does it even make sense to define a ”normal” and “the other” when you have only a couple people left over from the end of the world?

in this sense dirk is also an elaboration on kanaya, technically the first confirmed gay character in the comic. kanaya is, for all intents and purposes what we would call a lesbian, but the thing is “lesbian” as a label doesn’t exist in her culture. what she is seen as in her cultural context is someone with a really strong preference, the equivalent of having a type and only pursuing said type. troll culture around romance and the way it interacts with human culture around romance is in itself a critique of heteronormativity, a system with a bunch of silly labels and rituals which only hurts those who do not fit into it, but also hurt those that try to participate by systemitizing a number of social expectations aimed not at individual fulfilment but larger social goals.

dave says as much in his post retcon conversation with john and karkat: the concept of “gay” is just irrelevant at that point, and just a leftover of a bunch of social expectations and systems of a dead civilization and actively prescribing this systematized approach to sexuality oversimplifies and codifies what is in reality complex and somewhat nebulous.

TL;DR: rose never ”comes out” or is even confirmed as lesbian because that would pretty much go against the actual themes of homestuck as a story that is, all in all, pretty against systematizing and “charting” romance and love.