Toss mushrooms and pepper slices with olive oil and lightly coat with ranch dressing mix.
Place mushrooms and peppers on a shallow baking tray and place in oven until softened (approximately 10-15 minutes).
Remove mushrooms and peppers from oven, place one cap (or handful of baby bella slices) on one half of each kaiser roll, followed by the red pepper, arugula and then a slice of provolone cheese.
Lower the oven temperature to 200.
Wrap each slider individually with aluminum foil and place back into the oven until cheese is melted (approximately 5-10 minutes).