Add beef broth, onion soup mix, garlic powder and rosemary to Instant Pot and stir to combine.
Add in beef roast and place lid on Instant Pot and lock and seal the lid.
Click manual and high pressure for 45 minutes. When timer goes off, allow for the pot to naturally release some of it’s pressure (don’t vent until after 10-15 minutes)
After the 10-15 minutes, release any additional pressure in the pot and open. Take out the meat and shred.
Place meat on sub rolls and top with cheese. Melt under broiler for 2-3 minutes or until it’s reached your melt consistency.