Heat oil in a large skillet over medium high heat. Add onion and cook until softened, about 3 minutes. Stir in crumbled tempeh and cook 2 minutes more. Add sugar, garlic powder, and cayenne and stir for 1 minute.
Reduce heat to medium. Add bell pepper, zucchini, corn, red wine vinegar and soy sauce to skillet; cook for 3 minutes, stirring constantly. Add tomato sauce, tomato paste, salt, and pepper and cook 3-4 minutes more, until vegetables are softened, continuing to stir constantly. Spoon onto rolls to serve.
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