...it work with Rogers? Will putting a Rogers Wireless (Canada) SIM card into an AT&T phone make it work with Rogers? And is this considered unlocking a phone...or would unlocking the phone still be required?
Although they are the same network technically, just different names, you would have to unlock the phone itself to do that. And no, placing your SIM card into an AT&T phone is not considered unlocking it.
HI as Alex said without unlocking your phone from AT&T network you can't freely use it with rogers sim ..You can easily unlock your phone using sites like OnlineGsmUnlock.com here they are rendering unlock code for all mobile models at reliable cost ..After unlocking your phone you can freely use it with any GSM sim ...