Preheat the oven to 425 degrees F.
To a large casserole dish, add in the diced red onion, minced garlic, and green beans. Drizzle everything with the olive oil, and add on the salt, pepper, and red pepper flakes. Mix everything together until all of the vegetables are coated in oil.
Make a little nook in the center of the vegetables, and add in the Boursin cheese. Cover the dish with foil, and bake for 15 minutes.
After 15 minutes, remove the dish from the oven and remove the foil. Do NOT stir the Boursin in yet! Place the uncovered dish back in the oven for 10-15 more minutes, or until vegetables are slightly browned.
While the vegetables and Boursin are baking, cook your pasta in SALTED water. Before the pasta is done, reserve about 1/2 - 1 cup of the starchy pasta water and set aside.
Cook the pasta until it's al dente. After reserving the pasta water, drain the pasta and set aside.
Once the vegetables and Boursin are done roasting, take the dish out of the oven. Stir the vegetables and the Boursin together, adding in about 1/4 cup of pasta water. Then, add in the pasta and stir everything together, adding a few more small increments of pasta water if needed to smoothen the sauce. Add more salt, if desired.
Finally, stir in a handful of arugula and about 1/4 cup chopped fresh herbs, such as basil, chives, parsley, and/or oregano. Finish with a squeeze of fresh lemon juice. Top on with a little more black pepper and red pepper flakes, if desired.
Enjoy!