Assuming this will be the only starch and you are not going to have potato salad or pasta too....you will need about 20 cups of rice which will be about 8 pounds will yield about 50 cups of cooked rice.
You will need about 22 cups of liquid to cook with the rice. Or 5 1/2 quarts.
I would use at least 3 quarts of chicken broth...buy those boxes of Swanson's.
I don't know how you like your rice pilaf....but I would fry up onions green peppers, mushrooms and a lot of parsley and a couple of cans of diced tomatoes and at least 3 pound bags of frozen peas.
I would sautee 5 or 6 chopped onions in a fry pan with some oil....then fry up about 3 chopped green peppers and maybe 5 half pound boxes of mushrooms chopped.
I would put the broth into the roaster ( 3 qts) and measure the liquid from 3 large cans of chopped tomatoes and add that, then add 2 cups dry white wine and make up the rest with water.
When that comes to a boil I would add the rice and the cooked veggies, let it simmer for 15 minutes then add the drained tomatoes and about 1 1/2 cups chopped fresh parsley....and cook until the rice is done....about another 20 minutes.
Season to taste...salt....at least 2 teaspoons, depending on how salty the broth is...pepper? Do you like it spicy? perhaps add some red pepper flakes?
Then add the frozen peas and stir and keep warm until serving time.
You likely will have about 65 cups of finished rice....about 16 quarts.....might be best to divide the recipe and make it in 2 roasters so you can stir it and it won't spill all over.
Linda C

I often make jambalaya. When I made it in my Nesco huge roaster (not sure of the qt. size) it was way too moist, almost a gummy texture. I don't know if that's what you mean by "yucky". If so, perhaps if you cut back on the liquids in your recipe, you might have a drier pilaf.
Good Luck and have a fun party.