what are the advantages of roasting spices before use ?,?!

Best Answer - Chosen by Voters

dry roasting them makes them "sweat" and they release their vapours- they taste and smell so much better.
It's almost like opening a jar of salsa- you can smell it aswell.

Heating spices (by toasting, roasting, or sauteing) releases the flavors from the oily and/or hard skins, caramelizes them, and may also open them a bit if they're not crushed first.
Just crushing or grinding them (without heat) can also release more of their flavors than would happen if whole hard spices were used as is, but doing it just before using makes sure they're as fresh and full of oils/moisture as possible (no air, heat, light).

I find it better to just grind them right before use to release the oils and such.