Preheat your grill or smoker to 225 degrees F for indirect or two-zone grilling.
Remove the tops and ends of your vegetables, peel your sweet potatoes and get to slicing! Slice your vegetables into thin rounds, keeping the thickness as even as possible for all of your vegetables.
Pour your marinara sauce in the bottom of a 12 inch cast iron skillet. Smooth out with the back side of a spoon or spatula.
Arrange the vegetables in a repeating pattern of tomato, sweet potato, yellow squash, zucchini, on top of the sauce. I like to start on the outside edge of the pan and gently nestle the vegetables rounds into the sauce at a slight angle. Once you've completed one full circle around the outside edge of the pan, repeat with the second round, laying the vegetables down in the opposite direction. Once that circle is completed, arrange the final row in the middle of the pan and nestle a few additional pieces of vegetables around the middle row to fill in the empty spaces.
Drizzle the top of the vegetables with the olive oil and sprinkle evenly with the Grill Mates Roasted Garlic and Herb seasoning.
Place your skillet in your grill or smoker over indirect heat. Close the lid and cook for 2 hours. This will allow the vegetables to get nice and tender while picking up great flavor from the grill.
Increase the heat in your smoker to 375 degrees F, or if using a grill, slide your pan over to the direct heat side of your grill. This next step will take 30-45 minutes in a smoker, or it could go a little faster if you're using direct heat. Just keep an eye on the sauce in your pan to make sure it doesn't burn as the top of the vegetables are starting to caramelize.
Remove from the grill and let the ratatouille sit for 10 minutes or so. Garnish with fresh basil before serving.