I had some leftover Mexican roast beef and didn't really know what to do with it. I threw a bunch of stuff into a pan and simmered it for awhile. The mixture tasted wonderful! I had thought to make tacos, but then I got lazy, so I made it into a layered casserole instead. This is a very friendly versatile recipe as you can use leftover beef roast or pork roast, and vary your ingredients and spices to suite your tastes. Also, I like to make the casserole up in the morning, then toss it into the oven just before dinner time. Makes a hectic time just a little easier. Note: You can make a "Mexican" roast by cooking a roast in the crock-pot with salsa.