Preheat oven to 425 degrees. Grease two large baking sheets with nonstick cooking spray.
Heat the water in a microwave-safe container in a microwave on high for one minute 10 seconds. Add the flour mixture and yeast for the hot roll mix to a large mixing bowl. Stir well with a wooden spoon. Add the hot water and olive oil. Bring the mixture together with a wooden spoon.
When the dough has formed a ball and is cool enough to handle, transfer it to a flat, floured surface. Kneed the dough for 1-2 minutes, adding more flour as needed. You want the dough to be slightly sticky and not dry.
Divide the dough into two equal portions. Using a rolling pin, roll out each section of dough to fit a large baking sheet. The dough does not have to fit exactly. Folding each piece of dough into quarters, transfer them to the prepared baking sheets.
Poke the dough all over with a fork. Cover with a towel and let rise in a warm place for 15 minutes.
While the dough is rising, dice the vegetables, shred the cheese, and cook the sausage. To cook the sausage, grease a large frying pan with nonstick cooking oil. Remove the sausage casing and break the sausage into chunks as you add it to the pan. Cook over medium heat, continuing to break up the sausage as it cooks. Drain well.
When the dough is ready, spread the tomato sauce evenly over the dough, leaving a border around the edge for the crust. Cover the sauce with an even sprinkling of both garlic powder and oregano. Sprinkle 3 cups of mozzarella cheese and 1/8 cup Parmesan cheese over the sauce.
Layer the pepperoni slices and then cooked sausage. Layer the mushroom, pepper, and onion. Sprinkle the remaining cheeses.
Bake for 18 minutes, rotating halfway through, or until the crust is slightly browned and the cheese is bubbling.
Let sit for a couple of minutes before slicing with a pizza cutter. Serve immediately.
Notes
Refrigerate any homemade supreme pizza leftovers in a sealed container. Leftovers will keep for up to a week and taste great hot or cold.