Several hotels are available in the Rosemont area, please see the Big Ten Conference Center webpage.
The closest hotel is the Aloft Chicago O'Hare, a short walk away from the conference center. In general a rental car is not needed to get back and forth from O'Hare airport, the Aloft Chicago O'Hare hotel and the Big Ten Conference Center. A taxi is recommended to get from O'Hare to the Aloft hotel.