If you want to activate Free roaming service on Rogers network,First you will need to convert your sim network service from Fido to Rogers.
Before swap your network,Make sure your phone is unlocked.If it's network locked means,you will need to unlock your mobile.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 Unlock-Zone.com and you can get free unlock instructions from MobileUnlockGuide.com . After that you can easily activate Free roaming service with a help of rogers network.