I've heard add more water to the icing but how much piping gel would you add per cup to get smoother roses?

I haven't tried the piping gel, but you can add a tablespoon (more if ya need it) of crisco per cup of icing. The crisco helps make it more creamy and not as dry.

Adding water when it is dry is going to thin it down more than make it more creamy.

It should be 1/2 teaspoon piping gel to 1 cup icing. This works for thin when doing leaves and writting, and stiff for flower petals. Good Luck