Scrub sweet potatoes; pierce several times with a fork. Place on a microwave-safe plate. Microwave, uncovered, on high, turning once, until very tender, 7-9 minutes., When cool enough to handle, cut each potato lengthwise in half. Scoop out pulp. Spread onto half of each tortilla; top with beans and cheese. Fold other half of tortilla over filling., Heat a cast-iron skillet or griddle over medium heat. Cook quesadillas until golden brown and cheese is melted, 2-3 minutes on each side. Serve with salsa.