1. Each one of us has his room.
2. Each of us has his room.
3. We each have our room.
4. We each have our rooms.
(Are they all the same? Which one is correct #3 or #4?)
Are you only asking about 3 & 4? They are NOT the same. In 3, we each have one room. In 4, we each have more than one room.
Sra