Snow tires... LOL. Ive lived in Colorado almost my whole life and driven every Colorado winter since I turned 16 and have never... NEVER had a set of snow tires. I spent the last 4 years driving my 2wd ranger with the same all seasons that it came with from the factory. Ive had at least 3 2wd pickups while growing up and never needed dedicated snows. Ive also had various sports cars, SUV's, family cars and never needed snows on those either.
Now on my WRX, I picked up some Continental extremecontact all-season to replace the stock summers that come with the vehicle and I can honestly say it would be laughable to put snows on it unless I was headed way up into off beaten mountain territory and had to climb some gnarly 1/4 miles unplowed driveway. Decent all-seasons and common sense are all you really need, IMO.
Basically you just have to give yourself room, know your limits, understand how your vehicle reacts and use plain ass common sense.