The city of Bologna offers a wide variety of hotels.  Bologna is a very busy city but June is usually a good time to visit it since there is quite a low demand for hotel rooms for business at that time.
The conference organization will suggest from this page a list of possible accomodations of different costs, including some low-cost rooms in the University residence that will be provided on a first-come first-serve basis.

Follow the link to the Hello Bologna website for a general hotel search or to make a your own reservation online.