Heat oil in an over-proof skillet over medium-high heat.
Add the sausage and onion, and cook until lightly browned, about 6 minutes.
Add in the garlic, and cook for a minute longer. Add the white wine to deglaze, scraping up any browned bits. Allow to cook for about 5 minutes.
Add the broth, Ro-Tel, heavy cream, uncooked pasta and season with the pepper; Stir to combine. Bring mixture to a boil, cover, and reduce heat to medium-low. Simmer until the pasta is tender, about 15 minutes, stirring a few time while cooking to prevent sticking.
Preheat the broiler.
Remove the skillet from heat, and stir in the pepper-jack and 1/4 cup each of the cheddar cheese and Monterey Jack. Add salt if needed. Top with the remaining cheddar and Monterey Jack cheeses. Sprinkle the scallions on top.
Place skillet in the broiler and broil until the cheese is melted and lightly browned.