Well, to look at it from solely a financial point of view, a room in an apartment is worth much more if you rent it out by the night or week rather than by the year (like you would with a roommate).

Here in my neighborhood, in Chicago, one can find a room for about $40/night; 15 nights and I already have half my rent. So yes, having a roommate might be less work (but that depends on what you consider "work") but I can make more money renting a room out by the night.