Let's start by talking about their similarities. They both are made in a highball glass with ice, have grenadine syrup, and are garnished with a maraschino cherry. The differences are in the kind of soda used. Shirley Temple uses a lemon lime soda or ginger ale, and a Roy Rogers uses cola. Shirley Temples can also have orange juice in them, and can also be garnished with an orange wedge, wheel, or curl.