Preheat oven to 400°F and line a baking sheet with parchment. Spread cubed sweet potatoes evenly, drizzle with oil, and roast until tender and lightly browned, about 25 minutes.

In a large bowl, mash roasted sweet potatoes with black beans. Add garlic, red onion, cumin, chili powder, breadcrumbs, egg, salt, and pepper; stir into a cohesive mixture.

Scoop quarter-cup portions and shape into 2-inch sliders. Press edges gently to smooth. Place on a plate, cover, and chill 15 minutes.

Warm a tablespoon of oil in a skillet over medium heat. Add patties and cook until crisp and golden, about 4 minutes per side.

Split slider buns and toast cut-side down in the same skillet until edges turn golden, about 1–2 minutes.

Spread chipotle mayo on bottom buns, and layer patties with avocado slices, cilantro, and jalapeños.