Since the Roadmaster Classic doesn't have locking hard bags, it appears to be sold with the basic "no button" fob. However, you can still use the alarm feature without paying for a 2-button fob. If you firmly squeeze the fob approximately 1/2" below the small LED indicator (look at the end opposite the keychain), you will see the LED light. What you are doing is pressing the "lock" switch on the circuit board inside the fob. If you do this twice while in range of the bike, you will hear the bike honk - indicating the alarm is armed.I don't see anything on my key FOB to press. No buttons, switches, etc. How do you arm or disarm the alarm?
If the bike is moved or buttons pushed when the fob is out of range, the alarm will sound (horn honks and light flashes). To disarm the alarm, you can start the bike as normal with the fob in range or use your PIN code if the fob is not available.
Some people have drilled a small hole in the fob case above the switch and glued a little rubber button to make it easier to push; or you can buy the two-button fob and have the dealer pair it with the bike (your original fob will still work so you will have two fobs).