There are a few things you can do to secure your roll up garage door from the outside. First, you can install a lockset on the inside of the door that will engaged when the door is closed. This will prevent the door from being forced open from the outside. You can also install a deadbolt lock on the inside of the door that will engage when the door is closed. This will provide additional security against someone forcing the door open from the outside. Finally, you can install a security system that includes sensors on the doors and windows that will detect an intruder and sound an alarm.