I'll be making decorated sugar cookies for the first time this weekend, and I plan to use the NFSC recipe. My question is, how many batches of Alice's cookie icing would I need? It seems like the NFSC makes a lot since it requires 6 cups of flour, so would I need 2 recipes of Alice's icing? What about if I used Toba Garrett's Glace Icing? How much then? I need your help, experienced cookie makers!

Also... how thick should I roll the dough? I just received some rolling pin rings, and I'm trying to decide between 1/4" or 3/8". I should mention that I just plan to decorate the cookies simply, maybe just a solid colored background and a few piped details (pumpkin, ghost, and cat for Halloween). Stacking/hardness is not much of a factor since I am just bringing them to work.

Welcome to the wonderful world of cookies
I don't know about the icing recipe you are using but when I make Antonia's royal icing which uses a whole bag of icing sugar, it makes more than enough for the whole NFSC recipe. If you are just doing simple cookies you for sure should have enough. I use the rolling rings as well and use the orange ones - 1/4 inch thick I think . I find if I make them too thin I don't like the crispness of the cookie and I find you don't get a chance to appreciate the flavor and flakiness of the NFSC but that is just my opinion.
Good luck, you will do fine

I roll all my cookies to 1/4". Some like them thicker, so I don't think you'll go wrong either way. I use Toba's, but I've never made an entire recipe, so I don't know how far it will take you. I usually start with 3 cups of powdered sugar, 10 tsp. of milk, then 10 tsp. of cornsyrup. Add 15 drops of brite white food color. Divide and color according to what I'm doing. (The thickness of the icing will depend on the brand of powdered sugar you're using. Add just enough milk so there's no dry sugar left. It'll be a very heavy dough. Add the same amount of cornsyrup.) I think this recipe ices about (36) 3" cookies...but so much depends on how thin or thick you make the icing, and on how many colors you're using. Sometimes I'll make too much of one color, and have leftovers. Then I'll mix up more if I need a different color.

Good luck with your cookies! I got hooked about 6 months ago, and have become obsessed with decorating cookies!

If you've not made the NFSC before, please be aware that it is a good base, rather 'shortbreadish'. It is intended to take on whatever flavors and toppings you add.
If you want good flavor, you need to either double the vanilla, or add other flavoring to it. You can also flavor the icing.
We have people here who roll from 1/8" all the way to 1". It is very versatile.

Thanks, CC'ers are always so helpful...
Now I just have to decide on whether to use Toba's or Alices