Add the rice noodles to a medium saucepan filled with water and bring to a boil. Cook until tender, about 3 minutes. Drain, rinse with cold water and drain again. Divide the cooked rice noodles, bean sprouts and roast beef strips among 4 soup bowls.
Heat the oil in the same pan over medium heat. Add the jalapeno and scallions and cook, stirring occasionally, until softened, about 2 minutes. Add the beef broth and 2 cups water and bring to a boil. Cook, uncovered, for 10 minutes. Season the soup with salt and divide among the bowls. Garnish with the cilantro leaves and lime wedges.