I'm getting ready to brew my first sour next month and thought I'd see what people think of these different cultures. It's going to be a roughly lambic style brew (pils and wheat for the grist) and I'm going to pitch some 1056 along with one of these blends. That same night I'll be hosting a sour tasting and the dregs from a couple of the favorites will get tossed in as well. I planned on keeping the whole thing in primary (a better bottle) for the whole duration of fermentation (~ a year, depending on taste). Just wasn't sure what differences people have gotten from Lambic and Roeselare, as I know I've seen some people pitch the latter in a lambic style beer. Cheers!
My experience with Roselare vs the lambic blend is that the Roselare is more tart and fruity whereas the lambic blend gives you a little more funk. However, I imagine they can both be relatively unpredictable. Also, no need to pitch 1056. Both blends contain saccharomyces.
To be completely honest with you, I dont think it matters if you are planning on throwing dregs from different bottles in. Please know that im not saying there is no difference in these blends. From what I understand from my limited reading about these strains is that the Roeselare is more directed at recreating the spontaenous environment of west flanders. If you toss dregs in with either blend, you are altering the ratios of whats in those packs and you are going to have your own unique outcome. Also, dont waste the 1056, its redundant.
It sounds like you want to experiment, but given what you plan to do, I don't know if much can be said, since there don't seem to be sufficient controls on the experiment. If you want to see if you produce something discernibly different with one pitch vs the other, I would suggest splitting the batch and pitching each into separate containers, and not pitching any dregs. Then you will have something to evaluate at the end. I have a feeling that both would be a worthy final product, too, although my personal experience is limited to the Wyeast lambic blend.