I like the Fan of the Month format Rod.
There are a numer of roomies who will qualify for a number of entries and for multiple reasons, but I personally think that actually staging a '4 best roomies of the month' type approcah will dilute the objective of the competition.
Having said that, it wouldn't be out of order, as all the votes are collected, to announce 3rd, 2nd and 1st place results and offer prizes accordingly.
I like the competition immensely, its a great initiative and whatever the format, I would like to see it as a regular/monthly event.