BirchMarauder, I am far from an expert on forced induction, but maybe this will help a little:
With a Roots setup, the blower itself only moves air, it doesn't compress it; all of the compression, or "boost", takes place in the lower intake manifold. With a centrifugal blower like the Vortech and ProCharger, the blower unit actually compresses the air internally.
What all this means is that the Roots actually makes its highest boost almost right off idle, whereas the centrifugal type has to spool up to begin making significant boost levels, but, unlike the Roots, the boost doesn't fall off as RPMs increase, in fact it's the opposite: it just keeps right on building.
So to answer your question, you certainly could set up a centrifugal blower to have big boost at lower RPMs, but you would quickly run into an overboost situation as RPMs increased. The physics of the two units are different and they just don't act the same. This doesn't make one inferior to the other, they just have different strengths so pick the one that best suits your driving style.