At least for the first few waves of migration, I try to make sure every dwarf has his or her own bedroom. So each one gets a small room with a bed in it assigned to him or her. But the dwarves don't seem to take any notice of this: they all just sleep in whichever room they feel like!
Now, if this doesn't bother the owner of the room (I don't know whether it does) then I might as well just leave all the rooms unassigned and let the dwarves sleep wherever (this would save me a lot of room-assigning whenever a big wave arrives) and I probably wouldn't need as many rooms, since not everybody wants to sleep at the same time.
Is there a way I can force the dwarves to sleep only in their designated room or in the overspill/new migrant dormitory?
Best Answer
Dwarves will generally sleep wherever they see fit unless they have an assigned bed, in which case they will prefer this one. Sleeping in an assigned bed does give happy thoughts, being unable to makes a dwarf unhappy.
However, you don't generally have to bother with assigning beds since dwarves will claim unassigned bedrooms for themselves automatically.
Just a side-note: married dwarves and children share beds.