How would the dog boys react to butter roll (but I gave him dog ears)
Red Velvet would very probably dislike him for many reasons:
1: How Butter Roll treats Matcha. She's his sister and he cares about her. He's constantly making cakes and loves them all equally even if some come out "defective". Moreover, he's also different, even though in his case is more physical rather than psychological. From all people in the COD, Red Velvet wouldn't ignore nor treat badly Matcha because of being the way she is, so I think they would actually have a kinda close bond as siblings (Dark Enchantress adopted Red Velvet and Matcha was artificially created by her, so they're basically siblings xD).
So Matcha would actually open to Red Velvet and complain about how Butter Roll treats her, and also rant about many other stuff they don't tell him to keep him updated
2: Butter Roll feels like a replacement for him. As we know, Red Velvet is most of his time in the Tower, with zero contact with the outside world + the cakes are starting to fail more. So Dark Enchantress needed a new baker, a better one, and specifically one that knew about baking Cookies artificially (Cookies can only bake other cookies by using their own dough, aka they can only bake their children, probably because their own dough is the only source of life powder they have, but they can't create living Cookies from scratch). Yeah, Butter Roll specializes in creating homunculi :0. Dark Enchantress would probably want Red Velvet to be as ignorant of how things actually work in the outside world as she can, so she wouldn't even tell her Butter Roll being around is now a thing (Matcha is the one who ends telling him)
As friendly as he seems, Butter Roll has a lot of red flags, so if the other two notice how messed up he is after seeing that even Red Velvet despises him they would avoid him 😔.