Unless it is absolutely financially necessary that you have to live with a roommate, I'd suggest living alone. College is stressful enough with roommates - now add the even more stressful factors of grad school. The last thing that you are going to want to stress about is whether or not your roommate was mature enough to take out the trash when it was full, or they don't throw away their expire food, or they NEVER put the dishes in the dishwasher - god forbid they actually run the machine (I'm totally not speaking from 4 years of awful roommate experiences...).
I know at least for me, I am the type of person who likes to eliminate unnecessary stress in every form possible. So if you know that for any reason a roommate would stress you out, I would suggest living alone.