These companies still offer plenty of long-term upside for investors.The recent dip in the market indexes erased half the year's gains year to date, with the S&P 500 index up 9% on the year. But investors can take advantage of the sell-off to get better value on select companies with excellent growth prospects.Here's why three Motley Fool contributors believe DraftKings (DKNG -0.66%), Lyft (LYFT -3.08%), and Roku (ROKU -0.92%) are great stocks to buy right now.The momentum in online sports betting is realJo ...