No, Las Vegas is not in the Rocky Mountain Time Zone. It’s in the Pacific Time Zone (PT), which is one hour behind Mountain Time. For example, when it’s 3 PM in Denver (Mountain Time), it’s 2 PM in Las Vegas (Pacific Time).
The Pacific Time Zone (PST/PDT), which is UTC-8 during regular time and UTC-7 during daylight saving time, is where Las Vegas, Nevada is located. Pacific Time is one hour behind the Rocky Mountain Time Zone (MST/MDT).