I have cooked 3 regulators applying 12 V to RAW pin. Am I doing something wrong or did I get a bad batch?
The Pro Mini's 5V regulator (MIC5205) can supply a maximum of 150 mA, from which the Pro Mini uses about 20 mA, leaving around 130 mA for other applications.



Check the data sheet of the relay, to get the maximum current draw. For example, the RWH-SH-105D relay requires around 70 mA in the "on" position. While this is under the 130mA limit, you may be using other IOs or powering other modules.

To reduce the current draw, use a transistor to drive the relay like this: