Finishing a floor one room at a time is not a recommended practice. It takes several days, if not weeks for the polyurethane to completely cure. During that time, the poly will be off-gassing toxic volatile organic compounds (VOCs). Exposure to VOCs has been linked to many illnesses, and should be limited as much as possible. The VOCs will mostly dissipate within a few days, but there will be a slight odor for several days after that. The poly also will not achieve its full hardness until it fully cures, so you would want to keep traffic at a bare minimum while it is curing. You also want to keep the floors completely clear during this time because it is very easy to damage the finish.
Finishing one room at a time will only prolong the process of curing and out-gassing. The odor for the first couple of days would be nearly unbearable, and it is not recommended to be in the house immediately after the floor has been finished.
If you must do this one room at a time, be sure to keep the room closed off from the rest of the house. Make sure you have plenty of ventilation in the room, and keep the door closed for the first couple of days. You may want to also shove a towel in front of the door to block the fumes. If you have HVAC ducts in the room, those should be blocked off as well, so the fumes don't get blown through the entire house. You can block them off by either taping craft paper over them, or by blocking off the duct itself with a piece of foam, or a towel.
You should also bear in mind that doing one room at a time will make it more expensive to rent the equipment you need such as sanders. It is much cheaper to rent the equipment for a day, and get it all done at once instead of renting it for each room. By the time the dust settles, it may be just as cheap to hire someone to finish your floors professionally. The finished product usually comes out better when it is done by someone with experience. It is easy to damage the floor with the sander, if you aren't careful. Also, if you do not have room in your home to completely empty out these rooms, you can rent one of those portable storage sheds and have it delivered to your home.