A TRACON Controller reported Tower allowed aircraft to depart opposite direction into arrival traffic due to confusion during a runway configuration change.

Narrative

In the process of changing flows from south to north flow. The arrival end was vectoring to 04L and 03R the Tower departed two aircraft off of 21L opposite direction. Tower put the two aircraft on my frequency climbing via and on the SID. I had to turn both aircraft immediately to avoid a midair collision. The controller started to vector aircraft to the north runways even though the Tower still had two aircraft going to depart. The Tower Controller was not paying attention to what was happening and shipped the aircraft to my frequency as a normal departure. This is not the first time something like this has happened and it continues to get worst. What is the next incident going to be like? Recommendation: Don't allow the next one to happen and be an actual midair! The Tower needs to pay attention and look out the window and/or D-Bright. I've worked at D21 for a very long time; and I've never seen something so bad where I truly felt there was a possibility of a crash! Don't brush this under the rug!!!