Does a cell phone branded for AT&T work with a Rogers (Canada) sim card?

i plan on buying a phone from AT&T will it work with a roger's canada sim card or will i have to get the phone unlocked?

You will need to unlock it first.For unlocking you can approach your service provider or else try to buy an unlocking service from any one of the online unlocking service provider like TheUnlockArena.com Here you can unlock your phone at low cost.