Preheat oven to 400°F. Line a sheet pan with foil or parchment paper.
Slice sausage diagonally into coins. Cut potatoes (washed) into 1-inch pieces and slice onion into bite-sized chunks.
Add sausage, potatoes, and onions to a large bowl. Drizzle with olive oil and lemon juice, then add seasonings. Toss to coat evenly.
Pour mixture onto prepared sheet pan and spread into a single layer.
Roast for 25 minutes, then stir. Continue roasting for another 15 to 20 minutes, or until potatoes are fork-tender and golden around the edges.
Garnish with fresh chopped parsley and serve hot.
