Market sell-offs can sting, but they also create opportunities to make more money when stocks rebound. However, it's important to focus on buying shares of proven companies with a record of growth that still offer great long-term prospects.Three Fool.com contributors recently were asked to provide details on discounted stocks to buy right now. Shares of Shopify (SHOP -1.06%), RH (RH -4.29%), and Roblox (RBLX 2.08%) are all trading between 51% and 77% off their previous peak. Here's why these stocks could de ...