[Q] ROMs on Micro SD topic

I just got a Micro SD card today and have formatted it as NTFS (as suggested by Nvidia's Shield User Guide). The file structure is browsable and all appears well. However, the ROMs I have loaded onto it are not working despite them working perfectly fine if they are installed onto the built in memory.

I had previously read that ROMs worked off the Micro SD and would not have purchased a 64gb card otherwise. Is this possible without rooting the device? Please, help me get this working!