Not in the grand scheme, maybe a couple hundred pounds. The amount of force needed to roll you vehicle depends on the weight, and the rolling resistance of the tires. Weight is pretty straight forward, and rolling resistance ranges from ~.006 to .016, so a better bet would probably be LRR (low rolling resistance) tires, since you can likely see way more of a gain there. For instance, if your truck weighs 3500lbs, with the likely Crr of .010-.012, going to a LRR tire may net you a bigger gain. So
weight reduction-3300lbs*.012=39.6lbs
LRR tires- 3500lbs*.008=28lbs
I mean, it'll be an improvement, but it's better to go with LRR tires and have a full sized spare than the other way around.
edit- Ohhh, 4x4 eh? Run dual transfer cases so you can have really low highway OD gears, that could really improve mileage.