Place the beef in your crock pot and sprinkle with salt. Add the broth, chilis in adobo sauce, and ground cumin to a blender and blend until smooth. Pour this mixture into the crock pot and cover. Set on low for 8 to 12 hours.
When the barbacoa beef is ready, transfer the beef roast to a cutting board and use two forks to shred it. Transfer the shreds back to the crock pot for 15 minutes (or more) to absorb the juices.
If you love crispy barbacoa beef, heat a cast iron skillet to medium-high. Transfer some of the barbacoa beef (just enough for 1 layer) to the hot skillet and allow it to cook, stirring every 2 minutes or so, until the beef is nice and crispy, about 6 to 8 minutes total. Repeat this process until you have enough crispy beef for serving. If you're fine with tender shredded beef, you can skip this step and go straight to taco formation.
Heat up your choice of flour or corn tortillas. Load the tortillas up with barbacoa beef and micro greens, and top them off with Rojo's salsa.