Preheat the oven to 400°F. Grease a large sheet pan with cooking spray or line with parchment paper. In a large bowl add olive oil, Italian dressing mix, garlic powder and black pepper. Mix together to combine.
Add the cut potatoes to the bowl with the dressing and toss lightly to coat. Transfer the potatoes from the bowl to the sheet pan. Spread the potatoes evenly on the sheet pan, then bake in the oven for 20 minutes.
Slice the sausage into thick rounds and add it to the bowl with the excess dressing. Cut up the green beans and add them to the bowl as well. Combine the sausage and green beans in the bowl.
Take the potatoes out after 5 minutes of baking and flip them around. Add the sliced sausage and green beans to the sheet pan, and return it to the oven to bake for the remaining 15 minutes.
Remove from the oven when time is up, or when the potatoes are crispy, the sausage is a nice brown color, and the green beans are bright green. Scoop a serving off the sheet pan, and serve while hot!