Preheat the oven to 375 degrees.
Now, put the sliced mushrooms, sliced sweet peppers, chopped brussels sprouts and sliced sweet onions on a sheet pan.
Drizzle the olive oil over the veggies. Then sprinkle with the salt, garlic powder and pepper. Toss the veggies to coat them all with oil and the seasoning. Then spread them out evenly on the sheet pan.
Bake the veggies at 375 degrees for 30-40 minutes. Flipping the veggies after about 15 minutes. Bake them until they are nice and juicy and getting brown.
In the meantime, make the creamy french dressing. In a small mixing bowl, combine all of the dressing ingredients. Whisk to fully combine. Set aside.
Once the roasted veggies are done, remove them from the oven. Put the sub rolls in the oven for 1-2 minutes to toast them.
Then spread the sub rolls with creamy french dressing. Fill them with roasted veggies, then drizzle with more creamy french dressing. Serve immediately!