you can now receive calls on your rogers pay-as-you-go phone while travelling in the US. roaming in the US is now permitted for paygo customers. this is a recent development <2 months ago, ~ish>.
so just keep your rogers paygo phone on you. mind you, the roaming charges aren't cheap when receiving a call while in the US. it'll be $2.49/minute while receiving a call in the US, or making a call *from* the US *to* anywhere in the US or Canada.
hope that helps.