The number of hotels in Rome is countless. Only in one km range from the main Conference Venue (Sapienza University) there are more than 500 accommodation structures (hotels, bed and breakfast, guest houses). Termini and Policlinico subway stations are within walking distance from the University: so, any accommodation near to a subway line is convenient for congress delegates.
A partial list of hotels and guests houses near the conference venue is listed qui
In addition, congress delegates can visit the official website https://www.turismoroma.it/en
Some of the Congress participants may require visas in order to enter Italy. Please check with your local Italian Consulate or Embassy if you need a visa. All important information and application for visa forms can be found on the dedicated webpage of the Italian Ministry of Foreign Affairs, where a guided procedure will help you decide if you need to apply for a visa based on your nationality, country of residence, reasons for your visit and length of stay.