Preheat oven to 425°F. Line two baking sheets with aluminum foil or parchment paper.
Evenly divide Broccolini between prepared pans.
Drizzle with oil; sprinkle on garlic, salt, red pepper flakes, and black pepper.
Gently toss with your hands to distribute seasonings; spread out in a single layer.
Sprinkle with grated cheese; roast until golden brown, about 10-15 minutes.
Meanwhile, toast almonds in a dry, heavy skillet over medium heat, stirring constantly until golden, 1-2 minutes.
Remove from pan; allow to cool.
Sprinkle almonds over Broccolini; serve.