Funny... I'm in the process of making my own take of the so called Dokitale. The roles are different, as follows:
Natsuki's Papyrus, as she is very energetic and likes to cook, but not as much as Undyne does.
Sayori's Toriel since she lives with anxiety, and probably secludes herself because of that.
Yuri's Undyne because she's a Yandere, however, she DOES still have her shyness. This is meant to be irony, and it'll play a lot more of a role during the Undying fight.
Finally, Monika is Sans, due to her awareness of the game and it's timelines, and also for foreshadowing things that might happen later down the road. However, she can't control the files or the timeline, so she can't hurt anyone... Yet.
And that's all the role changes! I also plan to make a lot of original npcs and enemies, and also to change the story to make it a bit of a cross between Undertale and DDLC plotwise and lorewise.