One of my cousins recently graduated from NIT Arunachal Pradesh. He has shared his hostel experience with me:

• It all depends upon which hostel is assisted to you. If you are lucky you might get to live with 2-3 students or you will with at least 7 students in a single room. This is due to the unavailability of a permanent campus. 
• My cousin lived with 7 students who were allotted the same room. They were given 2 rooms, a hall with 2 bathrooms and a gallery. The distribution was such that 2 students in each room and the other 3 in the hall.
• By the 4th year, they were shifted to another building and 6 students were allocated the bigger room, and small rooms were allotted to 3 students.

You will get a better insight if you get in touch with any of the students currently studying in college.

Also, I don’t think rooms will be of any major concern. Once you get comfortable with your batch mates you will find a lot of empty beds to sleep in.