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I am going to make the assumption that Alexshock (OP) hasn't read the 2 web pages I pointed out - and that's why he hasn't posted back. But I am going to continue the conversation anyway.
First, I think even in extreme cases of stop and go traffic, rolling resistance is better for fuel economy than weight - because tires are such a small portion of the weight of the vehicle.
Also, the European regulations on tire labeling have a peculiarity about them. Rolling resistance varies by tire size, but the regulations do not take that into account. That means that you can get a tire with an A rating in one size and a C rating in the same make and model, but in another size. This is one of the reasons why the US hasn't issued regulations yet.
Also, there is technology triangle involving RR, treadwear, and traction. To get good values in one area, you have to sacrifice one or both of the others. And that is where the term "LRR" comes in. It means "Better RR compared to other tires with similar wear and traction characteristics.".
I know that sounds like a contradiction, but there are ways to improve RR while minimizing the impact to wear and traction. Suffice it to say that the term "LRR" is a relative term, not an absolute - so it shouldn't be a surprise to find a tire labeled "LRR" that doesn't have a good RR value - it's just better than other similar tires.
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