You’ll need for this: An iron griddle or tawa. Roasting in a heavy bottom pan is better as otherwise while roasting the cumin seeds tend to popup,creating a mess around.
Take the jeera/ cumin seeds on the warm griddle.Make sure the flame is on simmer. Keep stirring with a spoon while roasting.
Roast the jeera/ cumin seeds till they evenly turn brown.
Transfer to another plate or bowl till completely cooled doen.
Now, crush the jeera/ cumin seeds in a mortor-pestle till its powdered roughly.Store in an air tight container .
You can store this powder for a very long time without any change in the texture.