I know you are (rightfully) very excited to get Rodney home ...and we are all waiting to see that Cat Tax is paid ...but remember-
He'll need to carry on with whatever he's been eating in Rescue .
They might give you a couple of days worth to tide you over , but you'll need to make any changes slowly .
I put mine on grainfree biscuits over time , but they refused to change from Whiskas .(Grain free makes them smell less too)
He'll be going through many changes in the next few days - new house, new hooman to overlord , new bowls, new bedding . His guts need to keep the Status Quo
He might not be fussy with his litter - I put ours onto CatsBest , they were fine .
He might not use his tray for a couple of days ....but watch out when he does 
Ours have bowls with a scalloped edge to allow their short whiskas not to get caught . Some cats wouldn't bother but our Male whinged at me one evening "Mum this whisker/width ratio isn't working here" till I changed the bowl.
<<Shameless waiting for HomeComing Photos>>