Rose is one of those characters I find interesting since he’s morally ambiguous. While I agree the game does lean towards him ultimately being a good, if misguided person, his treatment of Bede stands out as offering a different interpretation of his character. That he actually is manipulative and isn’t a completely kind person. I stand by the mural scene at Stow-on-Side being a setup by Rose to get rid of a Bede, after he decided Bede had become more trouble than he was worth (sure, Bede blames Oleana during postgame, but who’s the one Oleana is doing the bidding of throughout the entire game).
Basically though, for this verse, I decided to go with the corrupt interpretation of Rose’s character. He picks up Bede from the orphanage partly because he sees potential in him as a trainer (thus useful to him in the future, especially if he were to become his puppet Champion) but also because he sees a cute, vulnerable boy who will be easy to manipulate into fulfilling his urges. He grooms Bede into thinking the things they do together behind closed doors are done out of love. Bede already admires Rose and feels indebted to him, so thinking that Rose loves him as well just further fuels his loyalty towards the man, being willing to do anything for him. A lot of my headcanons for this are actually based on art and fics I’ve seen that take this interpretation of Rose. Since this actually isn’t an uncommon interpretation of Rose and Bede’s relationship if you know where to look.
The events of the game plays out as in canon, Rose disowns Bede after the Stow-on-Side incident (nonsense happens in Hammerlocke with Bede trying to win back Rose’s favor), Opal rescues/abducts Bede to become her protege, and the Eternatus incident plays out as normal. Bede’s son with Rose, Roan, is actually conceived right before the Eternatus incident, during the Championship tournament.
Bede, after crashing the tournament and losing to Victor, remains in Wyndon. Unfortunately for him, his heat starts very shortly after this. In a moment of weakness, he goes to Rose Tower to seek out Rose, the man who he’d spent all his previous heats with. He’s both not entirely thinking straight, but he also isn’t over Rose at this point, even asking for Rose to take him back at some point during the encounter. Rose isn’t having any of that though, and isn’t even particularly kind to Bede during the incident. A big part of the reason Leon misses dinner with the protag and Hop isn’t because he was talking with Rose for hours, but rather because Rose made Leon wait hours to talk with him because he was busy having sex with Bede.
Rose turns himself in following the Eternatus incident and Bede eventually discovers that he’s pregnant. He knows right away who the father is, but for obvious reasons doesn’t tell anyone. As he spends more and more time with Opal, he also slowly comes to terms with just how wrong what Rose did to him was. Opal does find out who the father of Bede’s child is (she suspected all along, but Bede end up telling her the truth). Victor also finds out years later once he and Bede get together and Bede shares some of his past with him.
As for Rose, while he doesn’t care about Bede enough to keep tabs on him, he does make the connection that Bede’s son with the mystery father is his son. But for obvious reasons, he doesn’t do anything about it. Sends the occasional “anonymous” gift that Bede promptly throws away (rose seal on the letters is a dead giveaway). Roan doesn’t find out who his biological father is until he’s in his teens, which is the point Rose decides to personally enter the picture and tell Roan himself (leaving out many details of his and Bede’s past together, of course).
Syd and I came up with a fair chunk of this together, so the way things play out is basically the same in this verse. Just replace Roan’s name with Ambrose.