Do most universities and colleges apply roommates after you receive your housing assignment, or should I already know with both notifications? Not that I'd have a problem with no roommate, but I just find it a bit strange I don't know yet.
I don't know if this would be much help towards, but after searching your school site, I found this Housing Guide; http://www.housing.umass.edu/pdf/Guide to Residence Halls.pdf
I did find this;
Most students share double or triple rooms. Singles are assigned to students who have lived on campus the longest
To me it sounds like you should have a roommate, but to make sure call the Housing office for sure.