1-I want to know how many people there are in all of these rooms.
2-I want to know how many people there are in every one of these rooms.
3-I want to know how many people there are in each of these rooms.

Do all of these sentences mean the same?

I think "1" is ambiguous. It could mean the same as "3" and it could also mean:
4-I want to know all in all how many people there are in these rooms. (the total number of people)

Am I correct?

Gratefully,
Navi.