Wash the green beans well. After you wash them well, DRY THEM well. If they are still wet when they cook, they'll steam more than roast.
After they're nice and dry, clean up and trim any ends that need to be removed.
Now, grab a baking sheet. Throw the green beans onto the sheet. Drizzle with the olive oil and season with a generous amount of kosher salt and fresh ground pepper. With a pair of tongs, toss in the minced garlic and parmesan cheese until everything is well combined.
Into a preheated 400° oven the green beans go. Let them roast for 20-25 minutes. About halfway through cooking, toss them a bit to ensure even cooking.
Remove the green beans from the oven, top them with a generous squeeze of lemon, and enjoy!