"It could go on for another year or two," he said, speaking from the SALT Conference in Las Vegas.
"I see frothiness going to end up in nasty boom and bubble in asset prices, followed by crash and a bust, not this year, not next year, two years from now."
(Read More: Dow, S&P Hit New All-Time Highs )
On "Fast Money," Roubini cited a couple of factors: "Growth is slow. Earnings growth is also slowing down. Top line and bottom line are not as good as they used to be, but margins are high. They could correct somehow over time.
"But you have the gravitational forces of a slow economy leading eventually to correction, but then the levitational forces of QEs, zero policy rates, more money coming in the market, not just from the U.S. but other economies, is going to levitate asset prices."
(Read More: 'Cash Is Trash Right Now': Strategist )
Roubini said that those conditions could lead to "a generalized credit and equity and asset bubble next year or two, followed by a crash."
But, he added, "as long as the economy grows between 1Â½ to 2 percent and you have easy money, this market can go higher."
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