Olive oil in Crunchy Saffron Roast Potatoes

HI Lindsey, I'm planning to make Delia's roast potatoes and I notice in the original recipe she calls for dripping or lard but in the crunchy roast potatoes with saffron recipe she says to use olive oil. Is olive oil better when using saffron or could that recipe also be done with dripping or lard?

Also, not sure if you'll know the answer to this but I might as well ask - I have recently moved to New York from Ireland and all the potato strains are different so I no longer have my go-to spuds for various recipes - would you have any idea which american potatoes are best for roasting?

Many thanks
Sophie