The Federal Reserve will likely not raise rates later this year, a top economist told CNBC. And if the commodities market is any indication, it could be a long time before the central bank acts.

"I was always in the view that the Fed was going to be extraordinarily patient, and I still think they will be, but they don't have the smoking gun on runaway growth," David Rosenberg, chief economist for Gluskin Sheff said Thursday on CNBC's "Futures Now."

According to Rosenberg, a once noted bear who recently turned bullish, the real tell on when the Fed might hike rates will come in the form of rising commodity prices, not a traditional measure like wage inflation.

"Commodity prices are the inflationary impulse that usually picks up first," said Rosenberg. And in his eyes, "it's very rare to have the Fed start to raise rates with the CRB index making new lows." That index, which averages commodity futures prices, is trading near 52-week lows.

"I would say for the next several months use that as your [gauge] for what the Fed is going to do," he added. "My sense is it's going to be more of a story for next year than it is for this year."

With the Fed off the table for now, Rosenberg says it's all clear for stocks, even in spite of the recent volatility.

"I think that people that believe that a Greece exit or even problems in China are going to put anything more than a dent in the U.S. stock market should really start paying attention to history," he said.

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And Rosenberg pointed to what he called "the mother of all international collapses" in the period from 1997 to 1998 for comparison as reasons to stay bullish.

"When you go back to that period, emerging Asia was down 67 percent and through all the ups and downs and despite the intense jitters of the day, the U.S. market was up 15 percent," he said. "It makes what's happening in China look like a party."

Rosenberg expects the S&P 500 to end the year up at least 5 percent.