Start the cheese base: Add the cubed Velveeta and half of the undrained Rotel to a small heavy pot or Dutch oven set over low heat. Stir every minute until the cheese is mostly melted, 7–9 minutes.
Brown the sausage: While the cheese melts, cook the sausage in a large skillet over medium heat, breaking it up as it cooks, 5–7 minutes. If more than 1 tablespoon of fat remains, spoon off the excess.
Bloom the flavors: Stir in the minced garlic and cook 30 seconds. Sprinkle in the taco seasoning and cumin, then splash in 2 tablespoons of the liquid from the remaining Rotel. Stir until the sausage is evenly coated and the mixture looks glossy, about 1–2 minutes.
Combine and gently simmer: Scrape the seasoned sausage into the pot of melted cheese. Add the rest of the Rotel and switch the heat to medium-low. Stir until smooth and lightly bubbling, 2–3 minutes.
Finish and thicken: Turn off the heat, cover the pot, and let the dip rest 3 minutes to thicken before serving. Taste and adjust seasoning if needed.
Serve warm with sturdy tortilla chips, crackers, or fresh-cut veggies.