Originally Posted by SilvanoP
could i take a used Verison,AT&T etc, and after flash with some cooked ROM and using Italian SIM?
This has been asked and answered numerous times, so the ideal way to have found an answer - not mention a quicker one would have been to search the forum for existing threads.
What you are describing is called region locking
and is used to discourage black market sales of handsets intended for one region to another. You can purchase region unlock codes or even circumvent the region lock blacklist yourself on a rooted phone. For that matter, (limited) reports seem to indicate that SIM unlock codes also remove the region lock.