When does Lane Phase end?
In a game last night I was playing support. The ADC and I were doing very well, got first blood and took first tower. Granted it happened fairly quick, we got first tower at 9 minutes in. It was at that point, because we had a good wave, but not big enough to make it to the second tower, that I roamed to mid lane to help take that tower. My ADC kept pushing lane and got killed by the other duo. He tilts and goes off on me for leaving him during lane phase. I was always under the impression that if you get one tower and have your wave pushed, you should go help take towers in other lanes, or go for other objectives. Am I wrong, does lane phase last until a set time or when you reach a certain level? When does support start to roam?
TL:DR When does lane phase end and mid game/roaming/team fighting begin?