When I searched for roommates and wanted references, I was mainly looking to talk with people who had lived with the person...the main things I wanted to know were things like: did they pay rent on time, were they messy, did they come home drunk and mess up the house, did they have any annoying habits...basically, were they decent to live with, and were they responsible with rent (so I wouldn't have to pick up the slack for them if they skipped out on rent).
If you don't have anyone that fits that description (i.e. you've lived alone for a long time), I would recommend using a manager as a reference, as they can attest to similar things..you show up for work regularly, you haven't wandered in drunk, etc.
Good luck!