Jean Rosenbaum likes to start with an industry, and then go inside for companies that have the free cash flow and a strong balance sheet. Rosenbaum, who co-manages BlackRock U.S. Opportunities Fund , stays alert for stocks that perform best during the prevailing phase of the market cycle. Going into a downturn, for example, is when momentum stocks — those whose upward movement is driven largely by being popular — will get hit hard. A company that