Trim the rump roast (or beef) and cut it into large cubes. Set them into a large mixing bowl.
Add paprika, ancho, cayenne, garlic, onion powder and salt. Rub it vigorously into the meat.
Heat a large cast iron pan to medium-high heat and add olive oil.
Sear the rump roast on each side, a couple minutes each side. Be sure to get a nice, browned sear.
Add beer to the pan to deglaze. Stir to scrape up the brown bits from the bottom of the pan.
Pour it all into a slow cooker and cook about 5 hours, until the meat is fork tender.
Remove the roast from the cooker and cover.
Pour leftover juices from the slow cooker into a large pan and heat to medium.
Process the chipotles in adobo in a food processor until smooth. Add to the pan.
Swirl in flour and whisk to remove any lumps. Continue to cook a few minutes until the gravy thickens. Season with salt as desired.
Transfer the roast beef into the gravy and shred with forks. Stir to coat the beef nicely with the chipotle gravy.
Serve onto warmed tortillas with your fixings. Save the leftovers!