It is some time ago now, but I think when I went to the dorm shower with closes, undressed there and took a shower, the roommate partner stole them.
Then some days after that she (in my case) came to me in the shower and started with the dares.
I have no idea if this does anything for you but maybe it is worth a try.
Btw I feel you. It can be really annoying if you try to get something soecific in this game and it is just not working out as you hope.
I think those are 2 different things actually. 1 is the Roommate's Partner and the dares, but from what I understand there is something with the roommate, too.
The 1st is relatively easy, to get the dares the player character needs to masturbate when the roommate and their partner are having sex. Not sure if it's once or multiple times (I got the shower scene after the 2nd time) but that is a reliable way to get there. The Roommate's partner will "ambush" the player under the shower in the morning sooner or later, getting back at them for the masturbation thing. It's also the way to change the relationship into a more friendly one (at least stat wise, the game really doesn't handle dominance in combination with friendly very well at the moment).
What seems to be difficult is to get a scene where there's a sock on the doorknob or something when the player returns to their dorm and if they go inside they'll catch the roommate masturbating (from what I understood) and that opens up stuff with the roommate.