Once cool enough to handle, cut the corn off the cob and cut remaining vegetables into small pieces. Be sure your knife is very sharp, otherwise you will turn the tomatoes into a mush, soupy mess. Place all vegetables in a bowl (juice and all). Mix the cumin, garlic and lime juice together. Pour onto vegetables and toss gently. Salt and pepper to taste.
Sprinkle the thawed filets with your favorite seasoning. Scrub the grill with a wire brush to remove all grilling residue from the vegetables. Apply olive oil to the grates with an old towel or paper towel to prevent sticking. Place fish directly over coals or flame. Allow to cook for 4 to 5 minutes with the lid open. Gently turn and cook for another 3 minutes. Remove the fish and place on platter.
Place a piece of fish on a plate and pile some fire-roasted salsa on top. Obviously the salsa would go with almost any grilled fish, but I would encourage you to give swai a try.
Dave Lobeck is a barbecue chef from Sellersburg, Ind., who writes the "BBQ My Way" column for CNHI News Service. Visit his website at www.BBQ-My-Way.com.