I don't think Ohio State sold out any games last year, but they came close for a few times on Saturdays against big-time opponents. So I assume that means you can purchase tickets from the university, but as was mentioned, you might check to see if people are selling better tickets for a better value.
Yeah, someone told me that due to the nature of the arena and fan interest that OSU basketball games almost never sell out. MSU will be a big game, especially with OSU's success; however, it's not a prime Saturday afternoon game. It's like 9pm on a Tuesday.