Cook sweet potatoes: Pierce sweet potato with fork a few times. Place in microwave and microwave on high for 4-6 minutes or until cooked though. Once sweet potato is cooked, remove the skins and place potatoes in a medium bowl. Mash with a fork; set aside.
While potato is cooking in microwave, put sausage links in a pan and cook until brown.
In a separate large bowl, add black beans, cumin, chili powder and red pepper flakes if desired. Stir to combine then set aside.
To assemble burritos, make sure you have warm tortillas-it makes them easier to roll. You can warm them up for 10-20 seconds in the microwave before assembling. Lay out warm tortillas and evenly distribute and spread mashed sweet potato on each. Evenly distribute egg whites, diced avocado, black beans and sausage on each tortilla. Top with shredded cheese. Season with salt and pepper, if desired. Tuck ends in, then roll up burritos.