Tahini isn't just for hummus! Use the sesame seed paste as the base for the tasty sauce for these noodles.
Preheat the oven to 450°. Bring a pot of water to a boil for the pasta. On a baking sheet, toss the asparagus and oil; season with salt and pepper. Arrange in a single layer. Roast, turning once or twice, until browned in spots, 12 to 18 minutes.
In a bowl, whisk the tahini and 1/2 cup warm water; season generously. Mix in the lemon juice.
Salt the boiling water and add the pasta. Cook until al dente. Drain; return to the pot. Toss with the tahini sauce. Line a platter with radicchio leaves. Top with the pasta and asparagus. Finish with sesame oil, chili sauce, sesame seeds, and scallions. Serve with lemon wedges.