?can you flash rom from sd card topic

Quick question, can you install a custom rom from the sd card using twrp or does the rom need to first be installed in the internal storage before flashing? The reason I ask is that I was trying to install a rom from my sd card last night (brand new card) and the card fried. Was it a random event or is it not the right way to flash a rom onto this device?
Thanks in advance:)