Not sure whether ppl already posted for group exercise so I just quickly put something here.
I did it together with my on-campus interview. The whole experience was really great and exciting.. The 1-to-1 interview was quite conversational, but I heard some interviewers were more formal. The group exercise includes 2 parts, 1st part to tell a story for 1 min, 2nd part to present a "project" for 5 mins together with all team members. there were 6 ppl in my team. In both parts we presented to the two observers who were MBA2 student. It was really really fun... There is really nothing to prepare as all has to be spontaneous. I noticed the two observers were taking some notes during the whole session so I guess they needed to comments on each individual's behavior.
The team exercise was done in a pizza restaurant. So after that we were served with pizza and there were still MBA2 to come to talk to us. But I felt sorry for them as after the whole morning all of us were too tired and there were lot of awkward silent moments.
Overall I really enjoyed the days in Ross. It was a great experience and I actually learned a lot. As the applicants were exposed to the fellow applicants and students all the time, you will definitely make friends and learn something new.