Step 1: Preheat the Oven

Start by preheating your oven to 400°F (200°C). For easy cleanup and to prevent sticking, line a baking sheet with parchment paper or aluminum foil.

Step 2: Prepare the Potatoes

In a large mixing bowl, add your diced russet potatoes. Drizzle the 1/4 cup of olive oil over the potatoes and sprinkle in the ranch seasoning packet. Season with salt and pepper to taste. Toss the potatoes thoroughly, ensuring that each piece is well-coated with oil and seasoning.

Step 3: Bake the Potatoes

Spread the seasoned potatoes in a single layer on the prepared baking sheet. This ensures even cooking and crispiness. Place the sheet in the preheated oven and bake for 25 to 30 minutes, stirring halfway through to achieve an even golden-brown color. The potatoes should be crispy on the outside and tender on the inside.

Step 4: Add the Cheeses

Once the potatoes are done roasting, take them out of the oven and immediately sprinkle 1 cup of shredded cheddar cheese and 1/4 cup of grated Parmesan cheese evenly over the hot potatoes. Return the baking sheet to the oven for another 5 minutes, or until the cheese is melted, bubbly, and slightly golden.

Step 5: Garnish and Serve

After the cheese has melted to perfection, remove the potatoes from the oven. For an extra touch of freshness and color, sprinkle with chopped fresh parsley if desired. Serve immediately while the potatoes are still warm and cheesy.