The conference hotels, Hilton Portland Downtown and The Duniway Portland, both confirmed that they can split the bill any way you need: 50/50 or just split for the days that you and your roommate are sharing. You will need to provide your credit card to the Front Desk upon checking and let them know how the bill should to be split.
When you make the reservation online you can add your roommates name. If you have a reservation, you can add your roommate's name to the reservation by calling the hotel. If need be, you can also give your roommate your confirmation number, so they can check in without you present.
As a reminder, if you are staying more nights than your roommate, you will be responsible for these on your own. If you have any questions, feel free to call the hotel front desk:
Hilton Portland Downtown921 SW Sixth Ave.Portland, OR 972041-503-226-1611
The Duniway Portland545 SW TaylorPortland, OR 972041-503-553-7000
Dossier Hotel750 SW Alder StreetPortland, Oregon 972051-503-294-9000
The Heathman Hotel 1001 SW Broadway Portland, OR 972051-503-241-4100 We will match you up as quickly as possible, and you can always cancel your reservation if your roommate has a reservation also.