Rogers and T-Mobile are both GSM carriers, so you can install a Rogers 8320 OS on a T-Mobile. The only reason to do that would be if Rogers had released a different version of the OS than you have from T-Mobile. The Upgrade / Downgrade procedure in my sig will tell you how. Note that upgrading an OS is not difficult, but it is not trivial either, and you can easily make your phone inoperative if you don't know what you are doing, or misunderstand the instructions. If your phone is still in the 30-day return period, you should not change the OS, because you will have to put the T-Mobile OS back on if you return the phone.
