Can this be used for footers for a deck with a roof? If so how long do I have to wait once poured to start on the deck?

It would have to be mixed prior to pouring. The set time may cause cold joints if you cannot get it all poured at once. The pour would have to be all at once to keep a tight consolidated mix. The start time would be determined by the weight of the structure going in place vs. the psi of the material. This is calculated by a structural engineer. Use the datasheet and talk to your local Planning Department about how soon you can start building on the footers.