Welcome to Havoc's "Death Room" Theory classes.
Here is what I think about the "Death Room" in Yuno's house.
First of all, i would like to thank the person that allowed us to be here in the first place.
Thank you Yuno, for making the Death Room

Yuno: "Believe me, it was my pleasure!" *honest smile*
Havoc: "No doubt!"
Anyway, we all know what kind of dere is Yuno, and she is the honest personification of that dere.
What we know for sure is that there are several corpses in Yuno's house in the "Sealed Room"
We know that Yuno hated her family, she did express this vibe when Yuki's mother was around and Yuno slept in Yuki's room (she regretted probably that she was not IN the bed with him)
Yuno: "*stares*"
So getting back on topic, here are my observations, I seen something that looks like 5-6 corpses in that room, that means that there are at least her parents, and 3-4 other people in there.
My guess is, that at some point, Yuno was going to get raped or sold or whatever because of their parents debts, or just simply abused, one of the corpses is actually Yuno's neighbor that came by worried.
He was right to worry, but he was wrong to enter the house.
That is my current theory on the subject, what do you think miss Yuno?
Yuno: "Maybe you're right, maybe you're wrong!"
Yuno: " You have to wait and see!"
Yuno: *honest smile*