I have a 2007 550i that when I start the engine from a cold state, whether the weather is cold or warm the engine idles extremely rough or even backfires for 30 seconds to 1 minute. With a warm engine the idle is smooth from the start I've taken it to the dealer who clears out some codes, charges me a service call and tells me there's nothing wrong. Anyone with similar problems?

 

Hard to pin point with your description.
What is the difference between warmed up and cold? Well when it's warm parts expand, oil is thinner, the vanos behaves differently and pressure is higher.
I would suggest you ask the dealer for a list of the error messages you had at the time if the window is still open for that. Or get yourself a simple code reader like a V-checker its cheap and will give you codes with the interpretation. Just keep in mind there are proprietary codes which nothing but BMW softwares will read.