Guessing that there's some reason that they haven't told us yet because they said that there has never been a circumstance in which a sage has stayed behind.
Rose is my girl and I will be let down if it goes beyond her just acting out some of her developing feelings like saying she likes him and enjoys doing the lewd things. If being drunk is the shortcut to make her catch up to the other girls and have sex with Itsuki right now it would be really shitty.
I wonder sometimes, have any mangaka ever had any alcohol?
Like surely they have, yet they keep employing this trope where someone takes one sip and is instantly woozy. They alcohol hasn't even begun to enter the bloodstream...