Evenly coat a 7- to 8-inch omelet pan with spray. Add pepper, onion and seasoning. Cook, covered, over medium heat until peppers are soft, about 2 to 3 minutes.
Meanwhile, in small saucepan, stir together sauce and mushrooms. Cook over low heat until heated throughout. Keep warm while preparing omelet.
Pour eggs over pepper mixture. (Eggs should set immediately at edges.) With an inverted pancake turner, carefully push cooked portions at edges toward center so uncooked portions can reach hot pan surface, tilting pan and moving cooked portions as necessary. Reserving some sauce for topping, when top of omelet is thickened and no visible liquid egg remains, spoon hot sauce onto omelet in half or roll. Slide from pan onto plate. Spoon on remaining sauce.