In a medium skillet over medium heat, cook the ground beef, onion and garlic until onion is tender and beef is crumbled and no longer pink.
Add the tomato sauce, and oregano. Bring the mixture to a boil and reduce heat and simmer for about 8-10 minutes stirring occasionally until the sauce thickens up.
Place romaine lettuce on each roll and top with sloppy joe mixture and feta cheese.