Wireless networks provide a convenient means of seamless roaming services using portable consumer electronics communication devices (e.g., mobile devices, MDs), but ensuring robust security in wireless roaming is still challenging. However, to prevent wireless roaming services joining from malicious users/MDs, a secure and robust authentication model is highly desirable that can ensure adequate security. This paper exploits the concept of a delegation system and introduces a delegation-based robust authentication model for protecting wireless roaming services from unauthorized user – by means of portable communication devices (MDs). To perform robust authentication, the proposed scheme utilizes the biometric and defends roaming services from popular attacks and frauds. Security analysis is provided to guarantee that the proposed model provides unlinkability, and resists to denial-of-service and man-in-the middle attacks.