Here are some possibilities, but it's crucial to contact your veterinarian immediately:
* Strangles: A highly contagious bacterial infection affecting the upper respiratory system. Symptoms include a swollen throat, difficulty breathing, and fever.
* Abscess: A collection of pus that can occur in the neck due to infection.
* Laryngeal Hemiplegia: A condition affecting the larynx, which can cause a "roaring" noise.
* Trauma: A possible injury to the neck, such as from a kick or a bite.
* Other infections: Viral or bacterial infections can cause swelling and noise in the neck.
Remember: Never attempt to self-diagnose or treat a sick horse. Prompt veterinary attention is crucial for a speedy recovery.