Heat oven to 450°F. Season pork with salt and pepper. Place in a shallow roasting pan. Roast for 20 minutes, or until meat thermometer registers 160°F. Let stand 5 minutes. Cut into 1/2 inch-thick slices; cut slices into 1/4 inch-thick strips.
Meanwhile, bring a large pot of lightly salted water to a boil. Add vermicelli. After 2 minutes, add carrots. After 2 more minutes, add snowpeas. Cook for 1 minute longer, then drain, transfer to a large bowl, and toss with radishes, cilantro, and 1 teaspoon sesame oil.
In a small bowl, whisk together dressing ingredients. Drizzle remaining 2 tablespoons sesame oil in a slow stream, whisking until thickened. Pour all but 2 tablespoons dressing over noodles, and toss well to combine. Toss pork with the remaining 2 tablespoons dressing.