First, I need to understand what a ROM and NSP file are. ROMs are copies of original game cartridges or discs, right? NSP is a file format used by Nintendo for Switch game installations, especially through the Switch app. But legally, downloading ROMs without owning the physical copy is illegal. The user might be looking for a way to get the game or DLC for free, which is a gray area, especially if they don't own the Switch version.