It does not matter how many reminders of that bike on the roof you have. Human is very prone to miss something - miss to leave the opener at the house, miss to read the sign, miss to tape the button, miss to hear the bip(because of loud music or intense dialogue). You can't rely on warnings, simply because they are the same nature as remembering that the bike is on the roof - you have to remember to do something or not to do.

IMHO - the only way to prevent enetering the garage with the bikes is - do not enter the garage at all, when you approach the house. Period. Never.
You may put the car in the garage later, but not on initial approach.

Once you will know, that you never entered the garage for the last several months you will be able to tell, that you are on the new level - instinct, not your memory. And only then you are save. More or less.