ROCKY MOUNTAIN AIRWAYS FLT 2276 WAS ON A SCHEDULED FLT FROM DENVER, CO TO GUNNISON, CO. DURING TOUCHDOWN AT GUNNISON, THE RIGHT LANDING GEAR PARTIALLY COLLAPSED. THE CAPT WAS ABLE TO MAINTAIN DIRECTIONAL CONTROL DURING THE LANDING ROLL. HE TAXIED THE ACFT OFF THE RUNWAY ONTO THE ACFT PARKING APRON WHERE HE SHUT THE ENGINES DOWN AND THE PAX WERE DEPLANNED. SUBSEQUENT INVESTIGATION REVEALED THAT THE LOCK STRUT IN THE LANDING GEAR ASSEMBLY HAD FAILED DUE TO FATIGUE. A SERVICE BULLETIN REGARDING THE INSPECTION AND REPLACEMENT OF THIS PART HAD NOT BEEN COMPLIED WITH.