Thanks for writing!
Common ingredients that may contain gluten are rye, wheat, oats and barley, and noodles and pasta prepared with any of the previously mentioned grains. HVP, TVP, flavorings, are likely to contribute gluten as well, however, if they contain any gluten, the source would always be listed in the ingredient statements.
Since product formulations change from time to time, we do not have a printed list of products that identifies those products that contain specific allergens or gluten. The best advice we can give you is to check the ingredient list on the label. Ingredients allergens as defined by FDA: peanuts, tree nuts, soy, fish, seafood, wheat, eggs, and milk or dairy, as well as any ingredient that may contain gluten are always listed on the label.
Therefore, WE SUGGEST READING ALL INGREDIENT LABELS CAREFULLY.
We hope this information is helpful!
Your friends at Ragu
Note: I have never had a problem with the Ragu sauce I use for my made-from-scratch pizza. However, I always check the label to ensure nothing has changed since they indicate they will specifically list any gluten-containing ingredient on their label. You can find their FAQ here.