"Growth is not going to pick up and inflation actually is falling," the head of Roubini Global Economics and noted "Dr. Doom" told "Closing Bell." "So the markets are worried about tapering off sooner, but I think tapering off is going to occur later and therefore the market is going to rally." "You're going to have an increasing gap between Wall Street and Main Street, between what's happening to asset prices and real economic growth," he said. The effect of the Fed helping stock prices "for now is dominant, but of course over time it cannot trump those gravitational forces of economic fundamentals."