Rattus is a light, simple game of population growth, followed by violent population reduction at the hands of plague-ridden rodents. At the end of the game, the scoring conditions care neither for area control, majority control or any other type of population distribution. Only the person with the most people, aka little cubes, will emerge victorious.
There are 6 different "role" cards you can choose from, but these all also make you more sucseptible to the plague. Underneath each "rat" token likes some number of roles which translate into additional fatalities.
I have read that role selection in this game is actually a very deep process. Wheels within wheels, especially when you grab two roles and use the two special powers together in some synergestic way.
I have only had luck with a single combo of characters, the Merchant and the Monk. Apart, they are each ok. Together, they do a good job of winning.
The Merchant allows you to move a single group of up to 3 cubes from one reigon to an ajacient region. The Monk allows you to move a single rat token from one region to an ajacent region.
Because population can only be placed on regions with rats, and then only in the amount of rat tokens on the region, it pays to be able to dump a bunch of guys and then move them quickly to a plague-free region.
Any time I try anything else...the Peasant who adds additonal population cubes, the Witch who can look under rat tokens to see just how bad the fatalities are going to eventually be...I totally bomb out. The King seems very good at first, he can remove a cube to a palace "safe haven" where the plague can never strike. But I have seen other players using him, and they are still inevitably struck down by the Captain Merchant and Monk Boy.
I guess right now you could call Rattus a one-trick pony, but that's really only because I haven't figured out all the tricks. There are more tricks, I am confident!
There is also, according to reports, a strategy where you don't choose ANY role cards, and instead place your people to maximum effect and then look foward to the end-game when the plague strikes and few of your own cubes are removed. This does seem someone promising, if you are the most boring person in the world.
Otherwise, with the Merchant, at least you can move your guys around a little. People do it in Risk all the time, for FREE.