Take the cream cheese out of the fridge at least 30 minutes prior to starting the recipe so it has a chance to soften up. You can also microwave it for 20 seconds or so.
Boil a salted pot of water for the pasta and cook it al dente according to package directions.
Meanwhile, add the oil to a deep skillet over medium-high heat. Sauté the onion and peppers for about 5 minutes, stirring fairly often. I like the veggies tender-crisp, but you can cook them for a bit longer if you wish.
Reduce the heat to medium-low and stir in the Rotel, chicken broth, fajita seasoning, and cream cheese. The cornstarch in the fajita seasoning will thicken the sauce quickly (see note). Stir until the cream cheese has dissolved.
Add the cooked chicken in and let it warm through. If the sauce gets too thick, you can always thin it it out with some of the hot pasta water prior to draining it. Drain the pasta and toss with the sauce. Season with salt & pepper if needed and serve immediately.