RXR Realty has made a name for itself in recent years by scooping up large, regal office buildings in Manhattan, such as 75 Rockefeller Plaza and 340 Madison Ave. But as commercial real estate prices have surged back to pre-recession levels and investors feverishly compete for the trickle of trophy Manhattan properties hitting the market, the firm is shifting to a different investment strategy. It plans to spend $1 billion buying properties such as industrial warehouses in the Bronx, office buildings in Long Island City, Queens, and retail and residential space in St. George, Staten Island.