Why would my break pedal go to the floor and my car start to roll when I'm sitting at a stop light for a period of time? If im driving regular they work fine

The Master Cylinder is failing!!.. Constant, steady pressure on brake pedal will cause the fluid to bypass the piston in a failing master cylinder resulting pedal fall, quick or short term pedal application during normal (open road) driving will not!!..This is not a DIY repair..Leave it to a pro! Sorry but ..That's the breaks!

until you can afford a brake specialist look into doing it yourself it isnt that hard graba chiltons get some tools and read learn and fix but until you decide when you go to brake drop it to neutral as you approach the red light or stop signs as then the car wont pull forward and you wont have to use as much pressure on the brakes, that will help a bit. but make sure if they fail and they will that you dont drive to fast stop to fast and if they fail put it in neutral and grab the emergency brake and DONT KILL YOURSELF OR ANYONE ELSE. be careful