Avoid washing the mushrooms because they tend to hold a lot of moisture. Instead, wipe the mushrooms to clean off any dirt using a moist paper towel or cloth. Some of moisture will burn off when you roast them. Optional: I slice the stem down so it's flat and I have more pizza surface area.
Prepare a roasting pan or baking sheet with parchment paper or a non-stick mat. Place the mushrooms bottom-side up (so the inside is facing up) in the roasting pan.
Place any dry or fresh herbs on top of the mushrooms and then drizzle the olive oil and vinegar over each mushroom. Cover lightly with foil.
Roast the mushrooms for about 25 minutes, or until they become tender and you can stick a fork in them.
When the mushrooms are finished roasting, place all your toppings on them (with the cheese on the top), and bake for another 10 minutes at 400 degrees F, or until the cheese begins to bubble.