Brown the sausage in a skillet over medium heat. Drain off any excess grease.
Transfer the cooked sausage to a small slow cooker.
Add the undrained Rotel tomatoes and chilies, cream of mushroom soup, and milk to the slow cooker. Stir to combine.
Add the cubed processed cheese on top of the mixture. Do not stir yet.
Cover the slow cooker and cook on LOW for 2 to 3 hours, or on HIGH for 1 to 1.5 hours, stirring every 30 minutes until the cheese is completely melted and the dip is smooth.
Stir well before serving hot with tortilla chips or crackers.
Notes
For a spicier dip, use the hot variety of Rotel tomatoes.
You can prepare the sausage ahead of time and store it in the refrigerator.
If you do not have a slow cooker, you can combine all ingredients in a saucepan over low heat, stirring constantly until smooth.