Set a large saucepan over medium-high heat with the butter. Once melted, whisk in the flour and cook for about 30 seconds. Slowly whisk in the milk and cook until thickened, about 5 to 8 minutes. Season with salt, pepper, garlic, onion, and cayenne.
Remove from the heat and stir in the diced tomatoes, chiles and cheeses until melted through. Keep on very low heat until ready to serve.
Cook the soyrizo in a skillet, according to the package directions.
To serve, pour the cheese sauce into a round pie plate or casserole dish and smooth out into an even layer. Spoon the soyrizo on top in lines, mimicking the lines of a basketball. Serve immediately with salsa, guacamole and sour cream on the side and chips for dipping!