Traffic stop leads to discovery of firearms, narcotics, and explosive device in Arroyo Grande

By Atascadero News · Thu Oct 23 2025

SAN LUIS OBISPO COUNTY — On October 17, at approximately 3 a.m., San Luis Obispo County Sheriff’s Deputies conducted a traffic stop in the 600 block of Mesa View Drive. During the stop, deputies discovered drug paraphernalia, narcotics, and a firearm inside the vehicle.

Following the initial stop, deputies continued the investigation at a residence in the 600 block of Ralcoa Way in rural Arroyo Grande. Based on evidence collected and information from the scene, deputies and detectives from the Special Operations Unit obtained a search warrant for the property.

During the search, deputies recovered:

• Three firearms
• Approximately 6.3 ounces of suspected methamphetamine
• One Improvised Explosive Device (IED)

Upon discovery of the IED, the San Luis Obispo County Bomb Task Force was called to the scene. The device was safely removed and properly disposed of on-site.

Michael Rosso was taken into custody without incident and booked into the San Luis Obispo County Jail. He faces multiple charges, including:

• Felon in Possession of a Firearm (PC 29800(a)(1))
• Prohibited Person in Possession of Ammunition (PC 30305(a)(1))
• Possession of a Destructive Device (PC 18710)
• Possession of a Controlled Substance for Sale (HS 11378)
• Armed with a Firearm During Commission of a Felony (PC 12022(c))
• Possession of Drug Paraphernalia (HS 11364(a))

The investigation remains active, and the Sheriff’s Office encourages anyone with additional information to contact their Special Operations Unit.