Even though your rooted, here is what you will need to do, the issue is your phone number was change, it needs to be on a sense Rom, so if you still have a Nandroid of your Stock Rom then, first create a Nandroid of your current Rom, then restore your stock Rom, once that is done, do a Profile update, and then try your phone from there, if it still does not work, then you need to call Sprint and tell them you are getting a error message because you changed your number, they will send a refresh signal and then your phone will be back up and running. Once you have it back up and running, then you can restore your current Rom
FYI there is no need to tell them your phone is rooted, simply tell them you changed your number and did a factory reset and your phone will not connect, it is a common issues with their new set up