I haven't seen any scientific data that shows wide tires have lower rolling resistance. If that was really the case, you'd see people running 28s on track bikes. What the research has shown is that when inflated to give 15% deflection, wide tires maintain better traction on typical road surfaces and as a result you have less power loss to sliding friction. The better power transfer is more than enough to overcome the slightly higher rolling resistance, so wider tires end up being faster. But it's worth noting that once you have enough traction, having more is of no benefit so going even wider than that will start to cost some efficiency.
Of course all this is down in the noise compared to aerodynamic drag at typical road speeds. I'm only 145lbs yet I ride 25s on my CF bike and 28s on my Al frame. I'm probably sacrificing a couple of watts, but if I'm not racing that's a small price to pay for the added comfort.