The proven Zacks Rank system focuses on earnings estimates and estimate revisions to find winning stocks. Nevertheless, we know that our readers all have their own perspectives, so we are always looking at the latest trends in value, growth, and momentum to find strong picks.Of these, perhaps no stock market trend is more popular than value investing, which is a strategy that has proven to be successful in all sorts of market environments. Value investors use fundamental analysis and traditional valuation metrics to find stocks that they believe are being undervalued by the market at large.Zacks has developed the innovative Style Scores system to highlight stocks with specific traits. For example, value investors will be interested in stocks with great grades in the "Value" category. When paired with a high Zacks Rank, "A" grades in the Value category are among the strongest value stocks on the market today.One company value investors might notice is Beacon Roofing Supply (BECN). BECN is currently holding a Zacks Rank of #2 (Buy) and a Value grade of A. The stock has a Forward P/E ratio of 13.39. This compares to its industry's average Forward P/E of 21.58. BECN's Forward P/E has been as high as 17.80 and as low as 4.55, with a median of 12.95, all within the past year.Investors should also note that BECN holds a PEG ratio of 1.09. This popular metric is similar to the widely-known P/E ratio, with the difference being that the PEG ratio also takes into account the company's expected earnings growth rate. BECN's industry currently sports an average PEG of 1.72. BECN's PEG has been as high as 1.34 and as low as 1.01, with a median of 1.15, all within the past year.Value investors also use the P/S ratio. The P/S ratio is is calculated as price divided by sales. This is a prefered metric because revenue can't really be manipulated, so sales are often a truer performance indicator. BECN has a P/S ratio of 0.34. This compares to its industry's average P/S of 0.72.Finally, investors should note that BECN has a P/CF ratio of 8.25. This metric focuses on a firm's operating cash flow and is often used to find stocks that are undervalued based on the strength of their cash outlook. BECN's P/CF compares to its industry's average P/CF of 15.41. Over the past year, BECN's P/CF has been as high as 10.36 and as low as 2.85, with a median of 7.75.These are only a few of the key metrics included in Beacon Roofing Supply's strong Value grade, but they help show that the stock is likely undervalued right now. When factoring in the strength of its earnings outlook, BECN looks like an impressive value stock at the moment.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Beacon Roofing Supply, Inc. (BECN): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research