Lye rolls are a baked specialty in Germany (especially in Bavaria and Swabia), Austria, and Switzerland. They are made by glazing bread rolls with a lye solution before baking. The German name is Laugengebäck for any baked good dipped in lye, and for rolls specifically Laugensemmel or Kastanie (Bavarian), Laugenweckle (Swabian) or Laugenbrötchen (everywhere else in Germany); Laugenweckerl in Austria; Silserli or Laugenbrötli in Switzerland. In some parts of Asia they are known as Laugen Rolls.
In order to cause a Maillard reaction during baking for the characteristic browning effect, a lye roll needs to be coated with a high pH solution. The higher the pH, the stronger the reaction. Lye provides a high pH. However, lye is not the only way to produce this result, it's just the strongest and best for this purpose. A baking soda solution, which is easier to handle and arguably safer to use due to its lower pH, will provide a similar product but will not power as strong a reaction, so the effect will be less.
The same solution is also used for preparing pretzels; outside of Germany they are often the only baked food being commonly glazed with a lye solution.
Both lye rolls and pretzels are typically covered with large grains of salt. As a snack, lye rolls may also be sold covered with baked cheese, although this is more recent and less common. Typically they are cut in half and buttered, as large soft pretzels often are in Germany and Switzerland as well.