One of the most characteristic restaurants from Riaza is La Porticada. They are specialised in roasted baby lamb, wild mushrooms and beef from Sierra de Riazana. You will love its roasted pork because it is crunchy and juicy at the same time.
El Mesón de Las Columnas is also famous for its lamb and spoon dishes such as the callos which will warm you up in winter. The baby lamb ribs are delicious as well!
Another option is Ermita de Hontarares where they offer a short menu with traditional dishes: manitas de cerdo, saquitos de rabo de toro, etc. Wonderfull!!!