The term "PS Vita ROM" is a slight misnomer, but it has become the standard colloquialism in the emulation and console hacking communities. Strictly speaking, a ROM (Read-Only Memory) refers to a digital copy of a game from a cartridge-based system (like the Game Boy or Nintendo DS). The PlayStation Vita, however, used a proprietary flash memory card (a solid-state cartridge) and digital downloads.
If you're simply interested in playing PS Vita games without legal risk, buying a used Vita and physical games remains the safest, most straightforward method. If you're a preservationist or tinkerer, the homebrew route—with your own dumps—offers an incredible, near-flawless experience. roms ps vita