Heat oven to 425°F.
Trim the dry ends from the sprout and remove any yellow outer leaves, then halve the sprouts longitudinally.
Toss the sprouts with the olive oil and salt in a large bowl and spread in an even layer on a half-sheet pan, cut-sides down. Roast until the sprouts are lightly browned and tender, 20 to 25 minutes.
While the sprouts are still hot, toss in a large bowl with the sesame oil, fish sauce, red pepper flake, and roasted peanuts. Serve warm.